OMAP: Fix copy-paste bug that did not enable UART4 clock

V2 fixes line wrap issue of the patch itself.

UART3 was enabled twice instead of UART4.

One more cosmetic change in a comment on EMIF clock.

Signed-off-by: Lubomir Popov <lpopov@mm-sol.com>
Reviewed-by: R Sricharan <r.sricharan@ti.com>