drm/amdgpu: Add debugfs TA load/unload/invoke support

v1:
Add debugfs support to load/unload/invoke TA in runtime.

v2:
1. Update some variables to static.
2. Use PAGE_ALIGN to calculate shared buf size directly.
3. Remove fp check.
4. Update debugfs from read to write.

Signed-off-by: John Clements <john.clements@amd.com>
Signed-off-by: Candice Li <candice.li@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>