brcmfmac: add support for sysfs initiated coredump

The driver already supports device coredump initiated by firmware
event. Since commit 3c47d19f ("drivers: base: add coredump driver
ops") it is also possible to initiate it from user-space through
sysfs. This patch adds support for SDIO and PCIe devices.

Reviewed-by: Hante Meuleman <hante.meuleman@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>
Reviewed-by: Franky Lin <franky.lin@broadcom.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>