fix power descriptor value

The previous value would allow using the device
without external power, i.e. on a hub, which leads
to silent failures trying to power up the slots
(nothing happens, no atr will be received)

Change-Id: I40c48ea56151d13de362b8f73cae5b21aba0ebfa
FIXME: The device should offer at least one 100mA configuration.
diff --git a/sysmoOCTSIM/usb_descriptors.c b/sysmoOCTSIM/usb_descriptors.c
index 63ace0c..beb1633 100644
--- a/sysmoOCTSIM/usb_descriptors.c
+++ b/sysmoOCTSIM/usb_descriptors.c
@@ -52,7 +52,8 @@
 		.bConfigurationValue = CONF_USB_CDCD_ACM_BCONFIGVAL,
 		.iConfiguration = STR_DESC_CONFIG,
 		.bmAttributes = CONF_USB_CDCD_ACM_BMATTRI,
-		.bMaxPower = CONF_USB_CDCD_ACM_BMAXPOWER,
+		/* FIXME: The device should offer at least one 100mA configuration. */
+		.bMaxPower = 250, /* request 500mA */
 	},
 	.cdc = {
 		.comm = {