Revert "Makefile: add some optimization flags for ARM"

This reverts commit b85feced6c8e9e60717e1431d1867080ec648f8a.
Revert "Revert "Makefile: add some optimization flags for ARM""

This reverts commit 32a12efd9ba6ead19592635e39dedfd0b7165dda.
Revert "march armv7-a"

This reverts commit dc3855e0278ac8c64e60662a9c2a5fbfd70b8429.

Conflicts:
	arch/arm/boot/compressed/Makefile