Adds read-only SD driver, largely copied from ata-sd-pp.c
Only tested on the embedded SD, on the Clip
First steps to build a Normal firmware
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@19045 a1c6a512-1295-4272-9138-f99709370657
This way creation of scrolling thread doesn't risk crashing the system
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@19026 a1c6a512-1295-4272-9138-f99709370657