The RPM has two sets of selectors (IPC bit fields): request and
acknowledge. Apparently, some models use 4*32 bit words for select
and some use 7*32 bit words for request, but all use 7*32 words
for acknowledge bits.

So apparently you can on the models with requests of 4*32 select
bits send 4*32 messages and get 7*32 different replies, so on ACK
interrupt, 7*32 bit words need to be read. This is how the vendor
code apparently works.

Cc: stable@vger.kernel.org
Reported-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>