ANDROID: gki_defconfig: Enable CONFIG_RD_LZ4

Support future decompression of LZ4-compressed ramdisk images.

This support is in addition to the default support for gzip.

Bug: 150391496
Test: TreeHugger
Change-Id: I8c07e9363333c53cd6ff9c7e16fc42cbe318fe83
Signed-off-by: Alistair Delva <adelva@google.com>