wifi: brcmfmac: use strreplace() in brcmf_of_probe()

The for loop in brcmf_of_probe() would ideally end with something like
"i <= strlen(board_type)" instead of "i < board_type[i]".  But
fortunately, the two are equivalent.

Anyway, it's simpler to use strreplace() instead.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Suggested-by: Johannes Berg <johannes@sipsolutions.net>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/YqrhsKcjEA7B2pC4@kili