brcmfmac: drop unneeded function declarations from headers

Functions brcmf_c_prec_enq and brcmf_sdio_init don't exist so we
really don't need their declarations. Function brcmf_parse_tlvs is used
in cfg80211.c only so make it static and drop from header as well.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Acked-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>