ARM: bcm_defconfig: remove one level of menu from Kconfig

remove menu "Broadcom Mobile SoC Selection"
This requires:
- selecting ARCH_BCM_MOBILE based on SoC selections
- fixup bcm_defconfig to work with new menu levels.
- multi_v7_defconfig in another patch for merge purposes as per
Olof Johansson's request

Signed-off-by: Scott Branden <sbranden@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

arch/arm/configs/bcm_defconfig

@@ -25,7 +25,8 @@ CONFIG_MODULE_UNLOAD=y
 # CONFIG_BLK_DEV_BSG is not set
 CONFIG_PARTITION_ADVANCED=y
 CONFIG_ARCH_BCM=y
-CONFIG_ARCH_BCM_MOBILE=y
+CONFIG_ARCH_BCM_21664=y
+CONFIG_ARCH_BCM_281XX=y
 CONFIG_ARM_THUMBEE=y
 CONFIG_SMP=y
 CONFIG_PREEMPT=y