qcacld-3.0: Move SIGN_HEADER_MAGIC definition to BMI layer
FW common files needs to be in sync with host and fw.
SIGN_HEADER_MAGIC is not defined in fw common header files.
Abstract extra definition internal to host driver.
Change-Id: Ie902ca191617a6829c2cf3e6a45c3d170ae8d8c6
CRs-Fixed: 1012542