ARM: OMAP: Mask interrupts when disabling interrupts, v2

By Ingo Molnar, interrupts are not masked by default.
(refer to 76d2160147f43f982dfe881404cfde9fd0a9da21)

But if interrupts are not masked, the processor can wake up while in
Suspend-to-RAM state by an external interrupt. For example, if an
OMAP3 board is connected to Host PC by USB and entered to Suspend-to-RAM
state, it wake up automatically by M_IRQ_92. The disable_irq() function
can't disable the interrupt in H/W level, So I modified
arch/arm/mach-omap2/irq.c

Signed-off-by: Kim Kyuwon <chammoru@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>