msm: clock-local2: Correct the check for a null BCR_REG

The address passed into __branch_clk_reset is the
dynamically mapped base plus the register offset of a
BCR_REG. The wrapper reset op should check for a null
instead of this internal function, since the address
passed to the internal function will never be null.

Change-Id: I6c053408338bef8f1faa116ff651e62c4ed1cfd8
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>