ALSA: hda: tas2781-spi: Fix -Wsometimes-uninitialized in tasdevice_spi_switch_book()

Clang warns (or errors with CONFIG_WERROR=y):

sound/pci/hda/tas2781_hda_spi.c:110:6: error: variable 'ret' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
110 | if (tas_priv->cur_book != TASDEVICE_BOOK_ID(reg)) {
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
sound/pci/hda/tas2781_hda_spi.c:119:9: note: uninitialized use occurs here
119 | return ret;
| ^~~
sound/pci/hda/tas2781_hda_spi.c:110:2: note: remove the 'if' if its condition is always true
110 | if (tas_priv->cur_book != TASDEVICE_BOOK_ID(reg)) {
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
sound/pci/hda/tas2781_hda_spi.c:108:9: note: initialize the variable 'ret' to silence this warning
108 | int ret;
| ^
| = 0

Sink the declaration of ret into the if block and just return 0 at the
end of the function, as there is nothing to do if cur_book has already
been changed.

Fixes: bb5f86ea50ff ("ALSA: hda/tas2781: Add tas2781 hda SPI driver")
Reported-by: kernel test robot <[e-mail]>
Closes: https://lore.kernel.org/oe-kbuild-all/[e-mail]/
Signed-off-by: Nathan Chancellor <[e-mail]>
Link: https://patch.msgid.link/2025012[e-mail]
Signed-off-by: Takashi Iwai <[e-mail]>

sound/pci/hda/tas2781_hda_spi.c

···
 static int tasdevice_spi_switch_book(struct tasdevice_priv *tas_priv, int reg)
 {
 	struct regmap *map = tas_priv->regmap;
-	int ret;
 
 	if (tas_priv->cur_book != TASDEVICE_BOOK_ID(reg)) {
-		ret = regmap_write(map, TASDEVICE_BOOKCTL_REG,
-				   TASDEVICE_BOOK_ID(reg));
+		int ret = regmap_write(map, TASDEVICE_BOOKCTL_REG,
+				       TASDEVICE_BOOK_ID(reg));
 		if (ret < 0) {
 			dev_err(tas_priv->dev, "Switch Book E=%d\n", ret);
 			return ret;
 		}
 		tas_priv->cur_book = TASDEVICE_BOOK_ID(reg);
 	}
-	return ret;
+	return 0;
 }
 
 int tasdevice_spi_dev_read(struct tasdevice_priv *tas_priv,