firmware: qcom_scm: Add MODULE_LICENSE

qcom_scm.c was making modpost sad:

 WARNING: modpost: missing MODULE_LICENSE() in drivers/firmware/_qcom_scm.o

Change-Id: Ic0dedbad07455395082eba1da1e77063e7c66e17
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>