radeon_delay: Fix the return type of radeon_delay() helper

This function does not return a value. Change its return type to void.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
radeon_replay: Provide udelay function with trace output

This function is intended to be used instead of udelay(), as it
provides a trace output identical to radeon_delay().

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>