brcmfmac: remove pci shared structure rev4 support

brcmfmac: remove pci shared structure rev4 support

All pcie full dongle chips supported by fmac are using rev 5+ shared
structure. This patch removes the rev4 related code.

Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Reviewed-by: Arend Van Spriel <arend@broadcom.com>
Signed-off-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>