msm_bus: fix compilation when CONFIG_DEBUG_FS is disabled

Fix compilation error when CONFIG_DEBUG_FS is disabled in
perf_defconfig.

Change-Id: Id2f413362c5b34bbe099117b20b44721cbbb2ce5
Signed-off-by: Prateek Sood <prsood@codeaurora.org>
[rshaha@codeaurora.org: resolve trivial merge conflicts]
Signed-off-by: Rahul Shahare <rshaha@codeaurora.org>