malta: correct tcl script path in README.malta

README.malta referred to board/malta, but malta has now been moved
within board/imgtec/, so correct the path.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Daniel Schwierzeck <daniel.schwierzeck@googlemail.com>
Cc: Paul Burton <paul.burton@imgtec.com>

doc/README.malta

@@ -9,7 +9,7 @@ How to flash using a MIPS Navigator Probe:
 
   - Within Navigator Console run the following commands:
 
-      source /path/to/u-boot/board/malta/flash-malta-boot.tcl
+      source /path/to/u-boot/board/imgtec/malta/flash-malta-boot.tcl
       reset
       flash-boot /path/to/u-boot/u-boot.bin