Use parse-nhex

Instead of reimplementing it several times use parse-nhex to decode
two hex numbers,

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>

arch/sparc64/tree.fs

@@ -5,11 +5,7 @@ include config.fs
 \ -------------------------------------------------------------------------
 
 : decode-unit-upa ( str len -- id lun )
-  ascii , left-split
-  ( addr-R len-R addr-L len-L )
-  parse-hex
-  -rot parse-hex
-  swap
+  2 parse-nhex
 ;
 
 : encode-unit-upa ( id lun -- str len)

drivers/esp.fs

@@ -3,11 +3,7 @@
 \ -------------------------------------------------------------------------
 
 : decode-unit-scsi ( str len -- id lun )
-  ascii , left-split
-  ( addr-R len-R addr-L len-L )
-  parse-hex
-  -rot parse-hex
-  swap
+  2 parse-nhex
 ;
 
 : encode-unit-scsi ( id lun -- str len)

drivers/sbus.fs

@@ -3,11 +3,7 @@
 \ -------------------------------------------------------------------------
 
 : decode-unit-sbus ( str len -- id lun )
-  ascii , left-split
-  ( addr-R len-R addr-L len-L )
-  parse-hex
-  -rot parse-hex
-  swap
+  2 parse-nhex
 ;
 
 : encode-unit-sbus ( id lun -- str len)