cosmetic: fix typo in drivers/usb/Kconfig

This commit fixes a simple typo: sPL --> SPL.

Signed-off-by: Marc Ferland <ferlandm@amotus.ca>
diff --git a/drivers/usb/Kconfig b/drivers/usb/Kconfig
index fedc013..6e29119 100644
--- a/drivers/usb/Kconfig
+++ b/drivers/usb/Kconfig
@@ -60,7 +60,7 @@
 	  mode)
 
 config SPL_DM_USB_GADGET
-	bool "Enable driver model for USB Gadget in sPL"
+	bool "Enable driver model for USB Gadget in SPL"
 	depends on SPL_DM_USB
 	help
 	  Enable driver model for USB Gadget in SPL