fix BCD mask for date (Solaris 2.5 guest hang fix)

Fix BCD mask for date. The most visible effect of this patch is
Solaris 2.5.1 doesn't hang at boot if the day of month is >21.
Signed-off-by: NArtyom Tarasenko <atar4qemu@gmail.com>
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

hw/m48t59.c

@@ -239,7 +239,7 @@ void m48t59_write (void *opaque, uint32_t addr, uint32_t val)
         break;
     case 0x1FF5:
         /* alarm date */
-        tmp = from_bcd(val & 0x1F);
+        tmp = from_bcd(val & 0x3F);
         if (tmp != 0) {
             NVRAM->alarm.tm_mday = tmp;
             NVRAM->buffer[0x1FF5] = val;
@@ -310,8 +310,8 @@ void m48t59_write (void *opaque, uint32_t addr, uint32_t val)
         break;
     case 0x1FFD:
     case 0x07FD:
-        /* date */
-	tmp = from_bcd(val & 0x1F);
+        /* date (BCD) */
+       tmp = from_bcd(val & 0x3F);
 	if (tmp != 0) {
 	    get_time(NVRAM, &tm);
 	    tm.tm_mday = tmp;