ARM: pm: ensure ARMv7 CPUs save and restore the TLS register

Ensure that the TLS register is saved and restored over a suspend
cycle, so that userspace programs don't see a corrupted TLS value.

Tested-by: Kevin Hilman <khilman@ti.com>
Acked-by: Jean Pihet <j-pihet@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>