staging: brcm80211: remove unneccessary include from bcmsrom.c

Include statement of if_ether.h turned out to be unneccessary so
this is removed.

Reviewed-by: Henry Ptasinski <henryp@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>