Staging: brcm80211: remove Module.symvers file from the tree

This shouldn't have been in the tree, it's generated by the build, so
remove it.

Cc: Henry Ptasinski <henryp@broadcom.com>
Cc: Nohee Ko <noheek@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>