drm/amd/amdgpu: Fix style problems in amdgpu_debugfs.c

Fix the following issues reported by checkpatch:

WARNING: please, no space before tabs
WARNING: Prefer 'unsigned int' to bare use of 'unsigned'
WARNING: sizeof *rd should be sizeof(*rd)
WARNING: Missing a blank line after declarations
WARNING: sizeof rd->id should be sizeof(rd->id)
WARNING: static const char * array should probably be static const char * const
WARNING: Symbolic permissions 'S_IRUGO' are not preferred. Consider using octal permissions '0444'.
WARNING: Prefer seq_puts to seq_printf
ERROR: space prohibited after that open parenthesis '('

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