Check whether memory client reset is already asserted in order to prevent
DMA-flush error on trying to re-assert an already asserted reset.

This becomes a problem once PMC GENPD is enabled to use memory resets
since GENPD will get a error and fail to toggle power domain. PMC GENPDs
can't be toggled safely without holding memory reset on Tegra and we're
about to fix this.

Tested-by: Peter Geis <pgwipeout@gmail.com> # Ouya T30
Tested-by: Nicolas Chauvet <kwizart@gmail.com> # PAZ00 T20
Tested-by: Matt Merhar <mattmerhar@protonmail.com> # Ouya T30
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/20210119235210.13006-1-digetx@gmail.comSigned-off-by: Krzysztof Kozlowski <krzk@kernel.org>