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/ls1046aqds_lpuart_defconfig b/configs/ls1046aqds_lpuart_defconfig
index 282cb43..47636f1 100644
--- a/configs/ls1046aqds_lpuart_defconfig
+++ b/configs/ls1046aqds_lpuart_defconfig
@@ -25,7 +25,6 @@
 CONFIG_MP=y
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
-CONFIG_SYS_EXTRA_OPTIONS="LPUART"
 CONFIG_DYNAMIC_SYS_CLK_FREQ=y
 CONFIG_BOOTDELAY=10
 CONFIG_USE_BOOTARGS=y
@@ -93,6 +92,7 @@
 CONFIG_DM_SCSI=y
 CONFIG_DM_SERIAL=y
 CONFIG_FSL_LPUART=y
+CONFIG_LPUART=y
 CONFIG_SPI=y
 CONFIG_DM_SPI=y
 CONFIG_FSL_DSPI=y