arch-arm: Create a magic PendingDvm operand

JIRA: https://gem5.atlassian.net/browse/GEM5-1097

Change-Id: I38be0becc167d4d9764091aa46245508a0cc1ca4
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/56602
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/arch/arm/isa/operands.isa

@@ -419,6 +419,7 @@ def operands {{
     'SevMailbox': cntrlRegNC('MISCREG_SEV_MAILBOX'),
     'LLSCLock': cntrlRegNC('MISCREG_LOCKFLAG'),
     'Dczid' : cntrlRegNC('MISCREG_DCZID_EL0'),
+    'PendingDvm': cntrlRegNC('MISCREG_TLBINEEDSYNC'),
 
     #Register fields for microops
     'URa' : intReg('ura'),