drm/amd/display: fix for-loop with incorrectly sized loop counter (v2)

A for-loop is iterating from 0 up to 1000 however the loop variable count
is a u8 and hence not large enough.  Fix this by making count an int.
Also remove the redundant initialization of count since this is never used
and add { } on the loop statement make the loop block clearer.

v2: drop useless else (Walter Harms)

Addresses-Coverity: ("Operands don't affect result")
Fixes: ed581a0a

 ("drm/amd/display: wait for update when setting dpg test pattern")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>