[WHY]
Coverity analysis of the Upstream display driver code
(amd-staging-drm-next) flagged these three functions as
containing 'CONSTANT_EXPRESSION_RESULT' errors, i. e. the
conditionals are reduntant since their result is predetermined.

fixpt31_32.c:
The two flagged 'ASSERT' lines redundant since they are always true:
- LONG_MAX equals to the largest 'signed long long' number
- res.value is type 'signed long long',

So, the condition inside the 'ASSERTS's is always

link_dp_training.c:
The flagged conditional statement is always false:
- 'max_requested.FFE_PRESET.settings.level' is 4 bits, so its max
  possible value is 15
- 'DP_FFE_PRESET_MAX_LEVEL' equals to 15.

So, the conditional statement is always false and the wrapped code
never executes.

[HOW]
Removed lines flagged by Coverity analysis.
Reviewed-by: Sun peng Li <sunpeng.li@amd.com>
Acked-by: Zaeem Mohamed <zaeem.mohamed@amd.com>
Signed-off-by: Ivan Lipski <ivlipski@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>