aries: use uncompressed ramdisk

The kernel already performs LZMA compression on the whole ramdisk,
so compressing it once using gzip increases the size. Using
uncompressed ramdisk reduced the size from 7.4 MB to 5.4 MB.

Requires: https://gerrit.omnirom.org/7915

Build process warning
WARNING:  boot size (7475656) is 95.06% of limit (7864320)

Signed-off-by: Humberto Borba <humberos@gmail.com>
Change-Id: Iea3e3c991985718b1b30940ba4391bb425fc4281