brcmfmac: treat \0 as end of comment when parsing NVRAM

This fixes brcmfmac dealing with NVRAM coming from platform e.g. from a
flash MTD partition. In such cases entries are separated by \0 instead
of \n which caused ignoring whole content after the first "comment".
While platform NVRAM doesn't usually contain comments, we switch to
COMMENT state after e.g. finding an unexpected char in key name.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>