brcmfmac: remove brcmf_read_prof() function

The function brcmf_read_prof() provided access to fields
with brcmf_cfg80211_profile structure using a field id,
but the calling function can easily access that structure
directly. This patch removes the function.

Reviewed-by: Hante Meuleman <meuleman@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>