ALSA: hda - Allow fixed codec-probe mask

Some devices have broken BIOS and they don't set the codec probe-bit
properly after cleared by the driver.  This makes the driver skipping
the necessary codec slots.

Since BIOS update isn't always easy, now the semantics of probe_mask
option is changed a bit.  When it contains the bit 8 (0x100), the
lower bits are used to probe that slots regardless of codec-probe bits
returned by the hardware.

For example, probe_mask=0x103 will force to probe the codec slot #0
and #1.

Signed-off-by: Takashi Iwai <tiwai@suse.de>