arch-arm: gdb support Thumb-2 ISA

From the document*1, we should allow 2,3,4 in kind check function for
supporting all kinds of ARM breakpoint.

1. https://sourceware.org/gdb/current/onlinedocs/gdb/ARM-Breakpoint-Kinds.html

Change-Id: I82bcb88cfe6e80e7f17cd6bb68a26a45ace7b174
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/54124
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/arch/arm/remote_gdb.cc

@@ -168,6 +168,20 @@ namespace gem5
 
 using namespace ArmISA;
 
+namespace
+{
+
+// https://sourceware.org/gdb/current/onlinedocs/gdb/ARM-Breakpoint-Kinds.html
+enum class ArmBpKind
+{
+    THUMB = 2,
+    THUMB_2 = 3,
+    ARM = 4,
+};
+
+} // namespace
+
+
 static bool
 tryTranslate(ThreadContext *tc, Addr addr)
 {
@@ -364,8 +378,14 @@ RemoteGDB::gdbRegs()
 bool
 RemoteGDB::checkBpKind(size_t kind)
 {
-    // 2 for Thumb ISA, 4 for ARM ISA.
-    return kind == 2 || kind == 4;
+    switch (ArmBpKind(kind)) {
+      case ArmBpKind::THUMB:
+      case ArmBpKind::THUMB_2:
+      case ArmBpKind::ARM:
+        return true;
+      default:
+        return false;
+    }
 }
 
 } // namespace gem5