KVM: selftests: Change MDSCR_EL1 register holding variables as uint64_t

Change MDSCR_EL1 register holding local variables as uint64_t that reflects
its true register width as well.

Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: kvm@vger.kernel.org
Cc: kvmarm@lists.linux.dev
Cc: linux-kernel@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Acked-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Ada Couprie Diaz <ada.coupriediaz@arm.com>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20250613023646.1215700-3-anshuman.khandual@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Author: Anshuman Khandual

tools/testing/selftests/kvm/arm64/debug-exceptions.c

@@ -140,7 +140,7 @@ static void enable_os_lock(void)
 
 static void enable_monitor_debug_exceptions(void)
 {
-	uint32_t mdscr;
+	uint64_t mdscr;
 
 	asm volatile("msr daifclr, #8");
 
@@ -223,7 +223,7 @@ void install_hw_bp_ctx(uint8_t addr_bp, uint8_t ctx_bp, uint64_t addr,
 
 static void install_ss(void)
 {
-	uint32_t mdscr;
+	uint64_t mdscr;
 
 	asm volatile("msr daifclr, #8");