R600/SI: Also enable WQM for image opcodes which calculate LOD v3

If whole quad mode isn't enabled for these, the level of detail is
calculated incorrectly for pixels along diagonal triangle edges, causing
artifacts.

v2: Use a TSFlag instead of lots of switch cases
v3: Add test coverage

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=88642


Reviewed-by: Tom Stellard <tom@stellard.net>
llvm-svn: 228372