Fix SD-Card initialization process

After command ACMD41 was being sent we were not waiting
for the error idle state bit being cleared, so we were
really never going out from the initialization phase.

spi/mmc.c

@@ -424,7 +424,7 @@ DSTATUS disk_initialize(uint8_t drv)
                 while (MCF_SLT_SCNT(0) - target > 0)
                 {
                     res = send_cmd(ACMD41, 1UL << 30);	/* Wait for end of initialization with ACMD41(HCS) */
-                    if (res != 0xff)
+                    if ((res & SD_ERR_IDLE_STATE) == 0)
                         break;
                 }
                 debug_printf("res = %d\r\n", res);