armv8: ls1012a: Convert CONFIG_LS1012A to Kconfig option ARCH_LS1021A

Move this config to Kconfig option and clean up existing uses.

Signed-off-by: York Sun <york.sun@nxp.com>
CC: Calvin Johnson <calvin.johnson@nxp.com>
CC: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index aed89c9..c974db4 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -788,6 +788,7 @@
 
 config TARGET_LS1012AQDS
 	bool "Support ls1012aqds"
+	select ARCH_LS1012A
 	select ARM64
 	help
 	  Support for Freescale LS1012AQDS platform.
@@ -797,6 +798,7 @@
 
 config TARGET_LS1012ARDB
 	bool "Support ls1012ardb"
+	select ARCH_LS1012A
 	select ARM64
 	help
 	  Support for Freescale LS1012ARDB platform.
@@ -806,6 +808,7 @@
 
 config TARGET_LS1012AFRDM
 	bool "Support ls1012afrdm"
+	select ARCH_LS1012A
 	select ARM64
 	help
 	  Support for Freescale LS1012AFRDM platform.