thinkpad_acpi: Fix build error when CONFIG_SND_MAX_CARDS > 32

SNDRV_CARDS can be specified via Kconfig since 3.11 kernel, so this
can be over 32bit integer range, which leads to a build error.

Cc: <stable@vger.kernel.org> [v3.11+]
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>

drivers/platform/x86/thinkpad_acpi.c

@@ -6438,7 +6438,12 @@ static struct ibm_struct brightness_driver_data = {
 #define TPACPI_ALSA_SHRTNAME "ThinkPad Console Audio Control"
 #define TPACPI_ALSA_MIXERNAME TPACPI_ALSA_SHRTNAME
 
-static int alsa_index = ~((1 << (SNDRV_CARDS - 3)) - 1); /* last three slots */
+#if SNDRV_CARDS <= 32
+#define DEFAULT_ALSA_IDX		~((1 << (SNDRV_CARDS - 3)) - 1)
+#else
+#define DEFAULT_ALSA_IDX		~((1 << (32 - 3)) - 1)
+#endif
+static int alsa_index = DEFAULT_ALSA_IDX; /* last three slots */
 static char *alsa_id = "ThinkPadEC";
 static bool alsa_enable = SNDRV_DEFAULT_ENABLE1;