Revert "Revert "Inline ldrex/strex for thumb2, remove ARMv5 remnants.""

This reverts commit 5de4ed3c64cc7436c6a0744380a4f9c728454d2f.

Change-Id: Id65d3982cdd7d4af6b37f1e25170c9d6eadf4fbe
Signed-off-by: Marco Milanese <marcomilanese7@gmail.com>
atomic-arm.h: implement armv6 support

Change-Id: Ifdbaa0b8296e8df966dc2259b0a753f477c5ec69
Signed-off-by: Marco Milanese <marcomilanese7@gmail.com>