Convert CONFIG_LPUART et al to Kconfig

This converts the following to Kconfig:
   CONFIG_LPUART
   CONFIG_LPUART_32B_REG

And note that CONFIG_LPUART_32B_REG is unused in code.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/ls1021atwr_nor_lpuart_defconfig b/configs/ls1021atwr_nor_lpuart_defconfig
index 5bb3175..973b499 100644
--- a/configs/ls1021atwr_nor_lpuart_defconfig
+++ b/configs/ls1021atwr_nor_lpuart_defconfig
@@ -20,7 +20,6 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
-CONFIG_SYS_EXTRA_OPTIONS="LPUART"
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyS0,115200 root=/dev/ram0"
@@ -76,6 +75,7 @@
 CONFIG_DM_SCSI=y
 CONFIG_DM_SERIAL=y
 CONFIG_FSL_LPUART=y
+CONFIG_LPUART=y
 CONFIG_USB=y
 CONFIG_USB_XHCI_HCD=y
 CONFIG_USB_XHCI_DWC3=y