drm/msm: Fix undefined "rd_full" link error

rd_full should be defined outside the CONFIG_DEBUG_FS region, in order
to be able to link the msm driver even when CONFIG_DEBUG_FS is disabled.

Fixes: e515af8d

 ("drm/msm: devcoredump should dump MSM_SUBMIT_BO_DUMP buffers")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Rob Clark <robdclark@chromium.org>