board/microchip/mpfs_icicle/genimage.cfg: drop legacy gpt = true

Genimage complains about the config using the deprecated gpt option:

INFO: hdimage(sdcard.img): The option 'gpt' is deprecated.  Use
'partition-table-type' instead

So change to partition-table-type for consistency with the other configs.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Tested-by: Jamie Gibbons <jamie.gibbons@microchip.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

board/microchip/mpfs_icicle/genimage.cfg

@@ -15,7 +15,7 @@ image boot.vfat {
 
 image sdcard.img {
 	hdimage {
-		gpt = true
+		partition-table-type = "gpt"
 	}
 
 	partition uboot {