firmware: qcom_scm: Fix legacy convention SCM accessors

firmware: qcom_scm: Fix legacy convention SCM accessors

The move to a combined driver for the QCOM SCM hardware changed the
io_writel and io_readl helpers to use non-atomic calls, despite the
commit message saying that atomic was a better option. This breaks these
helpers on hardware that uses the old legacy convention (access fails
with a -95 return code). Switch back to using the atomic calls.

Observed as a failure routing GPIO interrupts to the Apps processor on
an IPQ8064; fix is confirmed as correctly allowing the interrupts to be
routed and observed.

Reviewed-by: Elliot Berman <eberman@codeaurora.org>
Fixes: c49b35848ac1 ("firmware: qcom_scm: Remove thin wrappers")
Cc: stable@vger.kernel.org
Signed-off-by: Jonathan McDowell <noodles@earth.li>
Link: https://lore.kernel.org/r/20200704172334.GA759@earth.li
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>