intel/compiler: Update block IPs once in dead_code_eliminate

Performance improvement in
dEQP-VK.ssbo.phys.layout.random.16bit.scalar.13 for n=30:

release build (w/Fedora build flags): -7.79% ± 0.25%
Meson -Dbuildtype=debugoptimized:     -5.10% ± 0.40%

The difference in the debugoptimized build is the calls to
inst_is_in_block(block, this) still exist on each call to remove().

v2: Only update each block's IP data once instead of once per block.
Suggested by Emma.

Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11632>

src/intel/compiler/brw_fs_dead_code_eliminate.cpp

@@ -121,7 +121,7 @@ fs_visitor::dead_code_eliminate()
             flag_live[0] &= ~inst->flags_written();
 
          if (inst->opcode == BRW_OPCODE_NOP) {
-            inst->remove(block);
+            inst->remove(block, true);
             continue;
          }
 
@@ -139,6 +139,8 @@ fs_visitor::dead_code_eliminate()
       }
    }
 
+   cfg->adjust_block_ips();
+
    ralloc_free(live);
    ralloc_free(flag_live);