[PATCH] powerpc: reorg RTAS delay code

This patch attempts to handle RTAS "busy" return codes in a more simple
and consistent manner.  Typical callers of RTAS shouldn't have to
manage wait times and delay calls.

This patch also changes the kernel to use msleep() rather than udelay()
when a runtime delay is necessary.  This will avoid CPU soft lockups
for extended delay conditions.

Signed-off-by: John Rose <johnrose@austin.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>