[MTD] replace MTD_ROM with MTD_GENERIC_TYPE

No mtd user should ever check for the device type.  Instead, device features
should be checked by the flags - if at all.
As a first step towards type removal, change MTD_ROM into MTD_GENERIC_TYPE.

Signed-off-by: Joern Engel <joern@wh.fh-wedel.de>

include/mtd/mtd-abi.h

@@ -25,10 +25,10 @@ struct mtd_oob_buf {
 
 #define MTD_ABSENT		0
 #define MTD_RAM			1
-#define MTD_ROM			2
 #define MTD_NORFLASH		3
 #define MTD_NANDFLASH		4
 #define MTD_DATAFLASH		6
+#define MTD_GENERIC_TYPE	7
 
 #define MTD_WRITEABLE		0x400	/* Device is writeable */
 #define MTD_BIT_WRITEABLE	0x800	/* Single bits can be flipped */