drm: msm: Check cmd_db_read_aux_data() for failure

We need to check the call to cmd_db_read_aux_data() for the error case,
so that we don't continue and use potentially uninitialized values for
'pri_count' and 'sec_count'. Otherwise, we get the following compiler
warnings:

   drivers/gpu/drm/msm/adreno/a6xx_gmu.c: In function 'a6xx_gmu_rpmh_arc_votes_init.isra.12':
   drivers/gpu/drm/msm/adreno/a6xx_gmu.c:943:12: warning: 'pri_count' is used uninitialized in this function [-Wuninitialized]
     pri_count >>= 1;
               ^~~
   drivers/gpu/drm/msm/adreno/a6xx_gmu.c:948:12: warning: 'sec_count' may be used uninitialized in this function
[-Wmaybe-uninitialized]
     sec_count >>= 1;
               ^~~

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: kbuild test robot <lkp@intel.com>
Cc: Jordan Crouse <jcrouse@codeaurora.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Evan Green <evgreen@chromium.org>
Cc: Jordan Crouse <jcrouse@codeaurora.org>
Cc: Rob Clark <robdclark@gmail.com>
Fixes: ed3cafa7 ("soc: qcom: cmd-db: Stop memcpy()ing in cmd_db_read_aux_data()")
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Andy Gross <andy.gross@linaro.org>
Acked-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Andy Gross <andy.gross@linaro.org>