qseeecom: Fix possible unused function

When building as a module, the __setup() macro is undefined and the
compiler will warn about the now unused setup function. Mark it as
__maybe_unused to avoid the compiler warning.

Change-Id: Ic0dedbad341aae7d83169517d94af3b0ea038ac9
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Zhen Kong <zkong@codeaurora.org>