drm/msm: fix address space warning

In the linux-4.19 stable kernel, we get a warning about a type
mismatch between phys_addr_t and dma_addr_t:

drivers/gpu/drm/msm/disp/dpu1/dpu_dbg.c: In function '_dpu_dbg_dump_dpu_dbg_bus':
drivers/gpu/drm/msm/disp/dpu1/dpu_dbg.c:2003:16: error: passing argument 3 of 'dma_alloc_coherent' from incompatible pointer type [-Werror=incompatible-pointer-types]
     list_size, &phys, GFP_KERNEL);
                ^~~~~
In file included from include/linux/dma-buf.h:31,
                 from drivers/gpu/drm/msm/disp/dpu1/dpu_dbg.c:20:
include/linux/dma-mapping.h:561:15: note: expected 'dma_addr_t *' {aka 'long long unsigned int *'} but argument is of type 'phys_addr_t *' {aka 'unsigned int *'}
   dma_addr_t *dma_handle, gfp_t flag)
   ~~~~~~~~~~~~^~~~~~~~~~
drivers/gpu/drm/msm/disp/dpu1/dpu_dbg.c: In function '_dpu_dbg_dump_vbif_dbg_bus':
drivers/gpu/drm/msm/disp/dpu1/dpu_dbg.c:2154:16: error: passing argument 3 of 'dma_alloc_coherent' from incompatible pointer type [-Werror=incompatible-pointer-types]
     list_size, &phys, GFP_KERNEL);
                ^~~~~
In file included from include/linux/dma-buf.h:31,
                 from drivers/gpu/drm/msm/disp/dpu1/dpu_dbg.c:20:
include/linux/dma-mapping.h:561:15: note: expected 'dma_addr_t *' {aka 'long long unsigned int *'} but argument is of type 'phys_addr_t *' {aka 'unsigned int *'}

This code was removed in linux-4.20 with upstream commit effec874792f
("drm/msm/dpu: Remove dpu_dbg"). Rather than backporting the large
patch, this just fixes the warning by using the correct type.

Fixes: 25fdd593 ("drm/msm: Add SDM845 DPU support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>