[arm64] Add missing DCHECKs in the assembler for movi.

NEONModifiedImmShiftLsl and NEONModifiedImmShiftMsl will also have a
DCHECK(is_uint8(imm)), however by that time we may have truncated the
uint64_t integer with a static_cast<int>.

Bug: v8:11033
Change-Id: Id0786e6525e385294748af6c77bdee4ca6db106c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2520901Reviewed-by: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Pierre Langlois <pierre.langlois@arm.com>
Cr-Commit-Position: refs/heads/master@{#71019}

src/codegen/arm64/assembler-arm64.cc

@@ -3210,9 +3210,11 @@ void Assembler::movi(const VRegister& vd, const uint64_t imm, Shift shift,
     Emit(q | NEONModImmOp(1) | NEONModifiedImmediate_MOVI |
          ImmNEONabcdefgh(imm8) | NEONCmode(0xE) | Rd(vd));
   } else if (shift == LSL) {
+    DCHECK(is_uint8(imm));
     NEONModifiedImmShiftLsl(vd, static_cast<int>(imm), shift_amount,
                             NEONModifiedImmediate_MOVI);
   } else {
+    DCHECK(is_uint8(imm));
     NEONModifiedImmShiftMsl(vd, static_cast<int>(imm), shift_amount,
                             NEONModifiedImmediate_MOVI);
   }