sdcard: Increase SDHCI_POWER_ON_TIME to 5ms

It appears some sd cards need additional time to initialize after
power on.

Reported-by: Chris <coderight@gmail.com>.
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
diff --git a/src/hw/sdcard.c b/src/hw/sdcard.c
index 6410340..ab7007b 100644
--- a/src/hw/sdcard.c
+++ b/src/hw/sdcard.c
@@ -128,7 +128,7 @@
 
 // SDHCI timeouts
 #define SDHCI_POWER_OFF_TIME   1
-#define SDHCI_POWER_ON_TIME    1
+#define SDHCI_POWER_ON_TIME    5
 #define SDHCI_CLOCK_ON_TIME    1 // 74 clock cycles
 #define SDHCI_POWERUP_TIMEOUT  1000
 #define SDHCI_PIO_TIMEOUT      1000  // XXX - this is just made up