Add option 'compress ramstage'

Add option 'compress ramstage'

Add an option to make compression of ramstage configurable. Right now
it is always compressed. On my Thinkpad, the complete boot to grub takes
4s, with around 1s required for decompressing ramstage. This is probably
caused by the fact the decompression does a lot of single byte/word/qword
accesses, which are really slow on SPI buses. So give the user the option
to store ramstage uncompressed, if he has enough memory.

Signed-off-by: Sven Schnelle <svens@stackframe.org>
Acked-by: Patrick Georgi <patrick@georgi-clan.de>
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@6552 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1