brcmfmac: assure active clock request upon entering SLEEP state

When the SDIO driver goes in low power state it must assure that
a clock request in ChipCLKCSR is set. Otherwise waking up the
device can fail. The register is read and if necessary the ALP
clock will be requested.

Reviewed-by: Daniel (Deognyoun) Kim <dekim@broadcom.com>
Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Reviewed-by: Franky (Zhenhui) Lin <frankyl@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>