global: Rename SPL_ to XPL_

Use XPL_ as the symbol to indicate an SPL build. This means that SPL_ is
no-longer set.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/usb/cdns3/Makefile b/drivers/usb/cdns3/Makefile
index 18d7190..d604785 100644
--- a/drivers/usb/cdns3/Makefile
+++ b/drivers/usb/cdns3/Makefile
@@ -4,8 +4,8 @@
 
 obj-$(CONFIG_USB_CDNS3)			+= cdns3.o
 
-cdns3-$(CONFIG_$(SPL_)USB_CDNS3_GADGET)	+= gadget.o ep0.o
+cdns3-$(CONFIG_$(XPL_)USB_CDNS3_GADGET)	+= gadget.o ep0.o
 
-cdns3-$(CONFIG_$(SPL_)USB_CDNS3_HOST)	+= host.o
+cdns3-$(CONFIG_$(XPL_)USB_CDNS3_HOST)	+= host.o
 
 obj-$(CONFIG_USB_CDNS3_TI)		+= cdns3-ti.o
diff --git a/drivers/usb/common/Makefile b/drivers/usb/common/Makefile
index 2e9353b..11cc465 100644
--- a/drivers/usb/common/Makefile
+++ b/drivers/usb/common/Makefile
@@ -3,7 +3,7 @@
 # (C) Copyright 2016 Freescale Semiconductor, Inc.
 #
 
-obj-$(CONFIG_$(SPL_)DM_USB) += common.o
+obj-$(CONFIG_$(XPL_)DM_USB) += common.o
 obj-$(CONFIG_USB_ISP1760) += usb_urb.o
 obj-$(CONFIG_USB_MUSB_HOST) += usb_urb.o
 obj-$(CONFIG_USB_MUSB_GADGET) += usb_urb.o
diff --git a/drivers/usb/dwc3/Makefile b/drivers/usb/dwc3/Makefile
index a46b682..a085c9d 100644
--- a/drivers/usb/dwc3/Makefile
+++ b/drivers/usb/dwc3/Makefile
@@ -6,11 +6,11 @@
 
 obj-$(CONFIG_USB_DWC3_GADGET)		+= gadget.o ep0.o
 
-obj-$(CONFIG_$(SPL_)USB_DWC3_AM62)	+= dwc3-am62.o
+obj-$(CONFIG_$(XPL_)USB_DWC3_AM62)	+= dwc3-am62.o
 obj-$(CONFIG_USB_DWC3_OMAP)		+= dwc3-omap.o
 obj-$(CONFIG_USB_DWC3_MESON_G12A)	+= dwc3-meson-g12a.o
 obj-$(CONFIG_USB_DWC3_MESON_GXL)	+= dwc3-meson-gxl.o
-obj-$(CONFIG_$(SPL_)USB_DWC3_GENERIC)		+= dwc3-generic.o
+obj-$(CONFIG_$(XPL_)USB_DWC3_GENERIC)		+= dwc3-generic.o
 obj-$(CONFIG_USB_DWC3_UNIPHIER)		+= dwc3-uniphier.o
 obj-$(CONFIG_USB_DWC3_LAYERSCAPE)	+= dwc3-layerscape.o
 obj-$(CONFIG_USB_DWC3_PHY_OMAP)		+= ti_usb_phy.o
diff --git a/drivers/usb/gadget/udc/Makefile b/drivers/usb/gadget/udc/Makefile
index 467c566..4b6a8fd 100644
--- a/drivers/usb/gadget/udc/Makefile
+++ b/drivers/usb/gadget/udc/Makefile
@@ -2,9 +2,9 @@
 #
 # USB peripheral controller drivers
 
-ifndef CONFIG_$(SPL_)DM_USB_GADGET
+ifndef CONFIG_$(XPL_)DM_USB_GADGET
 obj-$(CONFIG_USB_DWC3_GADGET)	+= udc-core.o
 endif
 
-obj-$(CONFIG_$(SPL_)DM_USB_GADGET)	+= udc-core.o
+obj-$(CONFIG_$(XPL_)DM_USB_GADGET)	+= udc-core.o
 obj-y += udc-uclass.o
diff --git a/drivers/usb/host/Makefile b/drivers/usb/host/Makefile
index 8dad36f..07deb4f 100644
--- a/drivers/usb/host/Makefile
+++ b/drivers/usb/host/Makefile
@@ -3,7 +3,7 @@
 # (C) Copyright 2000-2007
 # Wolfgang Denk, DENX Software Engineering, wd@denx.de.
 
-ifdef CONFIG_$(SPL_)DM_USB
+ifdef CONFIG_$(XPL_)DM_USB
 obj-y += usb-uclass.o
 obj-$(CONFIG_SANDBOX) += usb-sandbox.o
 endif