compression: test: Move into the lib suite

There is no particular need for compression to have its own test suite.
Move it into the lib suite instead.

Add the missing help for 'common' and update the docs.

Signed-off-by: Simon Glass <sjg@chromium.org>
Tested-by: Tom Rini <trini@konsulko.com> # rpi_3, rpi_4, rpi_arm64, am64x_evm_a53, am64-sk
3 files changed