otg: msm_otg: don't register USB supply in some cases

On some platforms it is not necessary to register a
power supply to report the USB status to user space.

Fix this by removing the section in code that registers
the power supply in all cases.

Change-Id: Ic07ac91708a07354e9c98f7cd9a91677a086b73b
Signed-off-by: David Keitel <dkeitel@codeaurora.org>