drm/amd/display: code cleanup on dc_link from is_same_edid to get_ddc_line

Removes codestyle issues on the file dc_link between is_same_edid and
get_ddc_line as suggested by checkpatch.pl.

Types covered:

CHECK: Blank lines aren't necessary after an open brace '{'
CHECK: Blank lines aren't necessary before a close brace '}'
WARNING: braces {} are not necessary for single statement blocks
CHECK: Comparison to NULL could be written
CHECK: Lines should not end with a '('
CHECK: Alignment should match open parenthesis
CHECK: Using comparison to false is error prone
CHECK: Using comparison to true is error prone
WARNING: Avoid multiple line dereference - prefer 'link->dpcd_caps.sink_count.bits.SINK_COUNT'
CHECK: Unnecessary parentheses around
WARNING: Missing a blank line after declarations
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>