Revert "[ia32,root] Disable root indirections in irregexp code"

This reverts commit fefd9230.

Reason for revert: breaks no-i18n 
https://ci.chromium.org/p/v8/builders/luci.v8.ci/V8%20Linux%20-%20noi18n%20-%20debug/23279

Original change's description:
> [ia32,root] Disable root indirections in irregexp code
> 
> Irregexp code spills and restores ebx at boundaries, and clobbers it
> inbetween. Root-relative loads are disabled in this region.
> 
> Bug: v8:6666
> Change-Id: I9c68bc8ef88d324da609996a8457ac9e30a9b6fc
> Reviewed-on: https://chromium-review.googlesource.com/c/1280762
> Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
> Commit-Queue: Jakob Gruber <jgruber@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#56639}

TBR=sigurds@chromium.org,jgruber@chromium.org

Change-Id: I1a349874c28218442ebed4f127d23d69dff094cd
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:6666
Reviewed-on: https://chromium-review.googlesource.com/c/1280225Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56643}

src/regexp/ia32/regexp-macro-assembler-ia32.cc

@@ -85,7 +85,6 @@ RegExpMacroAssemblerIA32::RegExpMacroAssemblerIA32(Isolate* isolate, Zone* zone,
     : NativeRegExpMacroAssembler(isolate, zone),
       masm_(new MacroAssembler(isolate, nullptr, kRegExpCodeSize,
                                CodeObjectRequired::kYes)),
-      root_is_clobbered_(masm_),
       mode_(mode),
       num_registers_(registers_to_save),
       num_saved_registers_(registers_to_save),

src/regexp/ia32/regexp-macro-assembler-ia32.h

@@ -178,9 +178,6 @@ class RegExpMacroAssemblerIA32: public NativeRegExpMacroAssembler {
 
   MacroAssembler* masm_;
 
-  // Irregexp code clobbers the root register.
-  NoRootArrayScope root_is_clobbered_;
-
   // Which mode to generate code for (LATIN1 or UC16).
   Mode mode_;