Revert "Makefile: Remove -march=armv7-a"

This reverts commit 0702904a4accea0d6e0a8acf47fdf1ec8f6845d4.
Revert "ARM: kconfig: select HAVE_EFFICIENT_UNALIGNED_ACCESS for CPUv6+ && MMU"

This reverts commit 770e2294711ebdc529cd5b224961af5932c7256d.