Make firmware header optional

[sbertrand-witekio]

With new firmware 429 and newer, header could be optional since CRC and pll_init_size are not used.

stehla@2e60df7#diff-2bb8fb9bfa2989b7871467dfd31e24f8728c7b5456b8140327ed45ed6a90286eR3084

	if (fw_hdr->magic != FW_MAGIC) {
		fw_data = (u8 *)fw_hdr;
		fw_size = ap1302->fw->size;
	} else {
		fw_data = (u8 *)&fw_hdr[1];
		fw_size = ap1302->fw->size - sizeof(*fw_hdr);
	}