ir3: Fix compress_regs_left accounting for half-regs

ir3: Fix compress_regs_left accounting for half-regs

This was just wrong - we need to check against the entire register file,
and we need to include removed full regs even if the register we're
trying to insert is a half-reg, or else we could run out of space when
reinserting full regs after it. There does need to be an additional
check so that we don't try to insert a half-reg beyond the half-reg
limit, but that has to happen in addition to the normal check.

This fixes KHR-GLES31.core.arrays_of_arrays.InteractionArgumentAliasing6
once spilling is added.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12033>