ALSA: fireface: code refactoring to handle model-specific registers

As a result of investigation for Fireface 800, 'struct snd_ff_spec.regs'
is just for higher address to receive tx asynchronous packets of MIDI
messages, thus it can be simplified.

This commit simplifies it.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/fireface/ff.h

@@ -36,7 +36,7 @@
 #define SND_FF_OUT_MIDI_PORTS		2
 
 #define SND_FF_REG_SYNC_STATUS		0x0000801c0000ull
-/* For block wriet request. */
+/* For block write request. */
 #define SND_FF_REG_FETCH_PCM_FRAMES	0x0000801c0000ull
 #define SND_FF_REG_CLOCK_CONFIG		0x0000801c0004ull
 
@@ -47,11 +47,6 @@ enum snd_ff_stream_mode {
 	SND_FF_STREAM_MODE_COUNT,
 };
 
-enum snd_ff_reg_type {
-	SND_FF_REG_TYPE_MIDI_HIGH_ADDR = 0,
-	SND_FF_REG_TYPE_COUNT,
-};
-
 struct snd_ff_protocol;
 struct snd_ff_spec {
 	const char *const name;
@@ -63,7 +58,7 @@ struct snd_ff_spec {
 	unsigned int midi_out_ports;
 
 	const struct snd_ff_protocol *protocol;
-	u64 regs[SND_FF_REG_TYPE_COUNT];
+	u64 midi_high_addr;
 };
 
 struct snd_ff {