Correct sandbox filesystem commands in FIT image test

The host filesystem name has changed, so update the tests. The tests now
run again correctly:

$ make O=b/sandbox sandbox_defconfig all
...
$ test/image/test-fit.py -u b/sandbox/u-boot
FIT Tests

=========
Kernel load
Kernel + FDT load
Kernel + FDT + Ramdisk load

Tests passed
Caveat: this is only a sanity check - test coverage is poor

Signed-off-by: Simon Glass <sjg@chromium.org>

test/image/test-fit.py

@@ -93,13 +93,13 @@ base_fdt = '''
 # then do the 'bootm' command, then save out memory from the places where
 # we expect 'bootm' to write things. Then quit.
 base_script = '''
-sb load host 0 %(fit_addr)x %(fit)s
+sb load hostfs 0 %(fit_addr)x %(fit)s
 fdt addr %(fit_addr)x
 bootm start %(fit_addr)x
 bootm loados
-sb save host 0 %(kernel_out)s %(kernel_addr)x %(kernel_size)x
-sb save host 0 %(fdt_out)s %(fdt_addr)x %(fdt_size)x
-sb save host 0 %(ramdisk_out)s %(ramdisk_addr)x %(ramdisk_size)x
+sb save hostfs 0 %(kernel_out)s %(kernel_addr)x %(kernel_size)x
+sb save hostfs 0 %(fdt_out)s %(fdt_addr)x %(fdt_size)x
+sb save hostfs 0 %(ramdisk_out)s %(ramdisk_addr)x %(ramdisk_size)x
 reset
 '''