pan/midgard: Remove "r27-only" register class

pan/midgard: Remove "r27-only" register class

As far as I know, there's no such thing as a load/store op that only
takes its argument in r27. We just need to set the appropriate arg_1
field in the RA to specify other registers if we want them.

To facilitate this, various RA-related changes are needed across the
compiler ; this should also fix indirect offsets which were implicitly
interpreted as "r27-only" despite not even passing through RA yet. One
ripple effect change is switching the move insertion point and adjusting
the liveness analysis accordingly, so while this was intended as a
purely functional change, there are some shader-db changes:

total instructions in shared programs: 3511 -> 3498 (-0.37%)
instructions in affected programs: 563 -> 550 (-2.31%)
helped: 12
HURT: 0
helped stats (abs) min: 1 max: 2 x̄: 1.08 x̃: 1
helped stats (rel) min: 0.93% max: 5.00% x̄: 2.58% x̃: 2.33%
95% mean confidence interval for instructions value: -1.27 -0.90
95% mean confidence interval for instructions %-change: -3.23% -1.93%
Instructions are helped.

total bundles in shared programs: 2067 -> 2067 (0.00%)
bundles in affected programs: 398 -> 398 (0.00%)
helped: 7
HURT: 4
helped stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
helped stats (rel) min: 1.54% max: 10.00% x̄: 5.04% x̃: 5.56%
HURT stats (abs)   min: 1 max: 2 x̄: 1.75 x̃: 2
HURT stats (rel)   min: 2.13% max: 4.26% x̄: 3.72% x̃: 4.26%
95% mean confidence interval for bundles value: -0.95 0.95
95% mean confidence interval for bundles %-change: -5.21% 1.50%
Inconclusive result (value mean confidence interval includes 0).

total quadwords in shared programs: 3464 -> 3454 (-0.29%)
quadwords in affected programs: 1199 -> 1189 (-0.83%)
helped: 18
HURT: 4
helped stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
helped stats (rel) min: 1.03% max: 5.26% x̄: 2.44% x̃: 1.79%
HURT stats (abs)   min: 2 max: 2 x̄: 2.00 x̃: 2
HURT stats (rel)   min: 2.56% max: 2.82% x̄: 2.63% x̃: 2.56%
95% mean confidence interval for quadwords value: -0.98 0.07
Inconclusive result (value mean confidence interval includes 0).

total registers in shared programs: 383 -> 373 (-2.61%)
registers in affected programs: 56 -> 46 (-17.86%)
helped: 12
HURT: 2
helped stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
helped stats (rel) min: 9.09% max: 33.33% x̄: 29.58% x̃: 33.33%
HURT stats (abs)   min: 1 max: 1 x̄: 1.00 x̃: 1
HURT stats (rel)   min: 20.00% max: 50.00% x̄: 35.00% x̃: 35.00%
95% mean confidence interval for registers value: -1.13 -0.29
95% mean confidence interval for registers %-change: -35.07% -5.63%
Registers are helped.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>