ARM: OMAP: Fix build breakage due to missing include in i2c.c

Merge commit 752451f0 ("Merge branch 'i2c-embedded/for-next' of
git://git.pengutronix.de/git/wsa/linux"

) resulted in a build breakage
for OMAP

  arch/arm/mach-omap2/i2c.c: In function 'omap_pm_set_max_mpu_wakeup_lat_compat':
  arch/arm/mach-omap2/i2c.c:130:2: error: implicit declaration of function 'omap_pm_set_max_mpu_wakeup_lat'
  make[1]: *** [arch/arm/mach-omap2/i2c.o] Error 1

Fix this by including the appropriate header file with the function
prototype.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Vaibhav Bedia <vaibhav.bedia@ti.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>