x86, defconfig: Add defconfig for Rambi audio development

Create a defconfig from kernel configuration I've used with Rambi. Has
framebuffer console, keyboard is working and audio drivers are built as
modules.

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
x86, rambi_test_defconfig: Disable SDHCI

MMC crashes when going to suspend and USB booting doesn't need it on Rambi
so disable it.

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>