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/ls1021aqds_nor_lpuart_defconfig b/configs/ls1021aqds_nor_lpuart_defconfig
index 56e00a7..43f93f4 100644
--- a/configs/ls1021aqds_nor_lpuart_defconfig
+++ b/configs/ls1021aqds_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_DYNAMIC_SYS_CLK_FREQ=y
 CONFIG_BOOTDELAY=3
 CONFIG_SILENT_CONSOLE=y
@@ -89,6 +88,7 @@
 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