regmap: add iopoll-like atomic polling macro

This patch adds a macro 'regmap_read_poll_timeout_atomic' that works
similar to 'readx_poll_timeout_atomic' defined in linux/iopoll.h; This
is atomic version of already available 'regmap_read_poll_timeout' macro.

It should be noted that above atomic macro cannot be used by all regmaps.
If the regmap is set up for atomic use (flat or no cache and MMIO) then
only it can use.

Signed-off-by: Sameer Pujar <spujar@nvidia.com>
Link: https://lore.kernel.org/r/1578546590-24737-1-git-send-email-spujar@nvidia.com


Signed-off-by: Mark Brown <broonie@kernel.org>