ALSA: hda - Load firmware in hda_intel.c

This is a preliminary work for the deferred probing for
request_firmware() errors at init.

This patch moves the call of request_firmware() to hda_intel.c, and
call it in the earlier stage of probing rather than
azx_probe_continue().

Tested-by: Thierry Reding <thierry.reding@avionic-design.de>
Reviewed-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>