tools: ffs-test: fix header values endianess

It appears that no one ever run ffs-test on a big-endian machine,
since it used cpu-endianess for fs_count and hs_count fields which
should be in little-endian format.  Fix by wrapping the numbers in
cpu_to_le32.

Cc: stable@vger.kernel.org
Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>