aco: Skip 2nd read of merged wave info when TCS in/out vertices are equal.

aco: Skip 2nd read of merged wave info when TCS in/out vertices are equal.

When TCS has an equal number of input and output, it means that the
number of VS and TCS invocations (LS and HS) are the same; and that
the HS invocations operate on the same vertices as the LS.

When this is the case, this commit removes the else-if between
the merged VS and TCS halves, making it possible to schedule
and optimize the code accross the two halves.

Totals:
SGPRS: 5577367 -> 5581735 (0.08 %)
VGPRS: 3958592 -> 3960752 (0.05 %)
Code Size: 254867144 -> 254838244 (-0.01 %) bytes
Max Waves: 1053887 -> 1053747 (-0.01 %)

Totals from affected shaders:
SGPRS: 29032 -> 33400 (15.05 %)
VGPRS: 35664 -> 37824 (6.06 %)
Code Size: 1979028 -> 1950128 (-1.46 %) bytes
Max Waves: 7310 -> 7170 (-1.92 %)

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4165>