drm/amdgpu: Fix ENOSYS means 'invalid syscall nr' in amdgpu_device.c

ENOSYS should be used for nonexistent syscalls only, replace ENOSYS with
EOPNOTSUPP for reset handlers that are not implemented for respective ASIC.

WARNING: ENOSYS means 'invalid syscall nr' and nothing else
+       if (r == -ENOSYS)

WARNING: ENOSYS means 'invalid syscall nr' and nothing else
+       if (r == -ENOSYS)

And other following style fixes in amdgpu_device.c:

WARNING: Symbolic permissions 'S_IRUGO' are not preferred. Consider using octal permissions '0444'.
WARNING: Block comments should align the * on each line
WARNING: Missing a blank line after declarations
WARNING: braces {} are not necessary for single statement blocks

Cc: Lijo Lazar <lijo.lazar@amd.com>
Cc: Kent Russell <kent.russell@amd.com>
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: Guchun Chen <guchun.chen@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>