i2c: OMAP: Fix OMAP1 build error

CONFIG_OF is not defined for OMAP1 yet and thus the omap1_defconfig build
generate an error for 3.3-rc1.

drivers/i2c/busses/i2c-omap.c: In function 'omap_i2c_probe':
drivers/i2c/busses/i2c-omap.c:1021:26: error: 'omap_i2c_of_match' undeclared (first use in this function)
drivers/i2c/busses/i2c-omap.c:1021:26: note: each undeclared identifier is reported only once for each function it appears in

Wrap omap_i2c_of_match with of_match_ptr() to prevent compilation error in case of OMAP1 build.

Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Cc: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>