cat: Fix main.ld typo to link romfs

Signed-off-by: C.W. Hsiao <cwhsiao.lionel@gmail.com>
romfs: update romfs header format

[NEW FORMAT]

|   32 bit   |   32 bit   |   32 bit       |   ?? bit   |   ?? bit   |
|    hash    |  data size | file name size | file data  | file name  |

Signed-off-by: C.W. Hsiao <cwhsiao.lionel@gmail.com>
test: fix SYS_OPEN fail by creating output folder

Signed-off-by: C.W. Hsiao <cwhsiao.lionel@gmail.com>
cat: add newline after filedump() finished

Signed-off-by: C.W. Hsiao <cwhsiao.lionel@gmail.com>