msm: ocmem: Do not return error when debugfs is disabled

The ocmem driver probe fails, when debugfs is disabled,
as it cannot create a debugfs root node. Do not return
and error, so that ocmem driver can function even when
debugfs is disabled

CRs-Fixed: 548301
Change-Id: I9dca715e9317d481b0dee1c7275c86a10e3cdce1
Signed-off-by: Neeti Desai <neetid@codeaurora.org>