drm/amd/display: Clean up style problems in amdgpu_dm_hdcp.c

[ Upstream commit a19de9dbb4d293c064b02cec8ef134cb9812d639 ]

Conform to Linux kernel coding style.

And promote sysfs entry for set/get srm to kdoc.

Suggested-by: Rodrigo Siqueira <[email protected]>
Cc: Rodrigo Siqueira <[email protected]>
Cc: Aurabindo Pillai <[email protected]>
Signed-off-by: Srinivasan Shanmugam <[email protected]>
Reviewed-by: Aurabindo Pillai <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>
Stable-dep-of: be593d9d91c5 ("drm/amd/display: Fix slab-use-after-free in hdcp")
Signed-off-by: Sasha Levin <[email protected]>

Author: srishanm