radeon_replay: Provide register access helpers

These helpers take the register number, rather than the register
address as a parameter, and thus match the representation in the atom
tables. Since they use the radeon_[read/write]_sync internally, they
provide identical trace output.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
radeon_replay/radeon_util.h: Provide bitwise set/clear function

This is much simpler to use than writing a read/modify/write sequence
every time we need to modify a register.