ARM: OMAP2+: Fix compiler warning for 32k timer

Commit "ARM: OMAP2+: Add device-tree support for 32kHz counter"
added structure omap_counter_match to the OMAP2 timer code. When
CONFIG_OMAP_32K_TIMER is not defined this structure generates the
following as it is not used.

  CC      arch/arm/mach-omap2/timer.o
  arch/arm/mach-omap2/timer.c:163:28: warning: 'omap_counter_match'
  defined but not used [-Wunused-variable]

Move the definition of omap_counter_match to avoid this warning when
CONFIG_OMAP_32K_TIMER is not set.

Thanks to Kevin Hilman for tracking down and reporting this problem.

Reported-by: Kevin Hilam <khilman@deeprootsystems.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>