[XFS] add dmapi miscdevice minor number

This doesn't mean dmapi is scheduled for inclusion, just adding
the reserved minor number to miscdevice.h for documentation purposes.

include/linux/miscdevice.h

@@ -18,6 +18,7 @@
 #define RTC_MINOR 135
 #define EFI_RTC_MINOR		136	/* EFI Time services */
 #define SUN_OPENPROM_MINOR 139
+#define DMAPI_MINOR		140	/* DMAPI */
 #define NVRAM_MINOR 144
 #define I2O_MINOR 166
 #define MICROCODE_MINOR		184