drm/amd/amdgpu/imu_v11_0: Increase buffer size to ensure all possible values can be stored

[ Upstream commit a728342a ]

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

 drivers/gpu/drm/amd/amdgpu/imu_v11_0.c: In function ‘imu_v11_0_init_microcode’:
 drivers/gpu/drm/amd/amdgpu/imu_v11_0.c:52:54: warning: ‘_imu.bin’ directive output may be truncated writing 8 bytes into a region of size between 4 and 33 [-Wformat-truncation=]
 drivers/gpu/drm/amd/amdgpu/imu_v11_0.c:52:9: note: ‘snprintf’ output between 16 and 45 bytes into a destination of size 40

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