OMAP4: clock: Fixing clock internal source selection for ABE ports

ABE ports need a mask of two bits in order to select the
correct internal source clock. This patch fix this mask that
was only one bit and was overlaping with source clock bits.

Change-Id: I8597efd9cec6707e815da39598a0adb7a3ce3c61
Signed-off-by: Israel Cepeda <icepeda@ti.com>
(cherry picked from commit a85258df4aa011cc65f6dab71f8b0d57d5b6f419)