Fix warning in arch/arm/mach-omap2/timer-gp.c

Fix warning in arch/arm/mach-omap2/timer-gp.c
arch/arm/mach-omap2/timer-gp.c: In function `omap2_gp_timer_set_mode':
arch/arm/mach-omap2/timer-gp.c:89: warning: enumeration value
`CLOCK_EVT_MODE_RESUME' not handled in switch

Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>