drm/amdgpu: Fix truncation in smu_v11_0_init_microcode

drm/amdgpu: Fix truncation in smu_v11_0_init_microcode

Reducing the size of ucode_prefix to 25 in the smu_v11_0_init_microcode
function. we ensure that fw_name can accommodate the maximum possible
string size

Fixes the below with gcc W=1:
drivers/gpu/drm/amd/amdgpu/../pm/swsmu/smu11/smu_v11_0.c: In function ‘smu_v11_0_init_microcode’:
drivers/gpu/drm/amd/amdgpu/../pm/swsmu/smu11/smu_v11_0.c:110:54: warning: ‘.bin’ directive output may be truncated writing 4 bytes into a region of size between 0 and 29 [-Wformat-truncation=]
  110 |         snprintf(fw_name, sizeof(fw_name), "amdgpu/%s.bin", ucode_prefix);
      |                                                      ^~~~
drivers/gpu/drm/amd/amdgpu/../pm/swsmu/smu11/smu_v11_0.c:110:9: note: ‘snprintf’ output between 12 and 41 bytes into a destination of size 36
  110 |         snprintf(fw_name, sizeof(fw_name), "amdgpu/%s.bin", ucode_prefix);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Suggested-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>