[media] staging: lirc: Improvement in code readability

There is no need to call kfree() if memdup_user() fails, as no memory
was allocated and the error in the error-valued pointer should be returned.

Signed-off-by: Shailendra Verma <shailendra.v@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>