brcmsmac: remove brcmsmac own sprom parsing

brcmsmac now takes the sprom from bcma and do not uses its own sprom
parsing any more. Remove this code as it is not used any more.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Tested-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>