ARM: omap2+: rename config to ARCH_OMAP2PLUS and consolidate Kconfig

In Linux, CONFIG_ARCH_OMAP2PLUS is used for OMAP2 or later SoCs.
Rename CONFIG_ARCH_OMAP2 to CONFIG_ARCH_OMAP2PLUS to follow this
naming.

Move the OMAP2+ board/SoC choice down to mach-omap2/Kconfig to slim
down the arch/arm/Kconfig level.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/omap3_overo_defconfig b/configs/omap3_overo_defconfig
index 0fa05cb..daea034 100644
--- a/configs/omap3_overo_defconfig
+++ b/configs/omap3_overo_defconfig
@@ -1,13 +1,14 @@
 CONFIG_ARM=y
+CONFIG_ARCH_OMAP2PLUS=y
+CONFIG_SYS_MALLOC_F_LEN=0x2000
 CONFIG_OMAP34XX=y
 CONFIG_TARGET_OMAP3_OVERO=y
+CONFIG_SPL_STACK_R_ADDR=0x82000000
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
 CONFIG_VERSION_VARIABLE=y
 CONFIG_SPL=y
 CONFIG_SPL_SYS_MALLOC_SIMPLE=y
-CONFIG_SPL_STACK_R_ADDR=0x82000000
 CONFIG_SPL_STACK_R=y
-CONFIG_SYS_MALLOC_F_LEN=0x2000
 CONFIG_SPL_MTD_SUPPORT=y
 CONFIG_SPL_OS_BOOT=y
 CONFIG_HUSH_PARSER=y