drm/amd/amdgpu/amdgpu_sdma: Increase buffer size to account for all possible values

drm/amd/amdgpu/amdgpu_sdma: Increase buffer size to account for all possible values

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/amd/amdgpu/amdgpu_sdma.c: In function ‘amdgpu_sdma_init_microcode’:
 drivers/gpu/drm/amd/amdgpu/amdgpu_sdma.c:217:64: warning: ‘.bin’ directive output may be truncated writing 4 bytes into a region of size between 0 and 32 [-Wformat-truncation=]
 drivers/gpu/drm/amd/amdgpu/amdgpu_sdma.c:217:17: note: ‘snprintf’ output between 13 and 52 bytes into a destination of size 40
 drivers/gpu/drm/amd/amdgpu/amdgpu_sdma.c:215:66: warning: ‘snprintf’ output may be truncated before the last format character [-Wformat-truncation=]
 drivers/gpu/drm/amd/amdgpu/amdgpu_sdma.c:215:17: note: ‘snprintf’ output between 12 and 41 bytes into a destination of size 40

Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>