OMAP3: PM: Use ARMv7 supported instructions instead of legacy CP15 ones

On ARMv7 dsb, dmb instructions are supported and can be used directly
instead of their cp15 equivalnet. Also remove the opcodes for smc
and use the available instruction directly in OMAP3 low power asm code

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>