n_smux: Fix compilation when CONFIG_N_SMUX is undefined

Fix compilation issues when CONFIG_N_SMUX is undefined and
empty stub functions are getting defined.

Change-Id: I6a9982dac7d9558b8da533f1fc28dddac6c1f8fc
Signed-off-by: Angshuman Sarkar <angshuman@codeaurora.org>
1 file changed