x86/xen: silence smatch warning in pmu_msr_chk_emulated()

Commit 8714f7bc ("xen/pv: add fault recovery control to pmu msr
accesses") introduced code resulting in a warning issued by the smatch
static checker, claiming to use an uninitialized variable.

This is a false positive, but work around the warning nevertheless.

Fixes: 8714f7bc ("xen/pv: add fault recovery control to pmu msr accesses")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

arch/x86/xen/pmu.c

@@ -302,7 +302,7 @@ static bool xen_amd_pmu_emulate(unsigned int msr, u64 *val, bool is_read)
 static bool pmu_msr_chk_emulated(unsigned int msr, uint64_t *val, bool is_read,
 				 bool *emul)
 {
-	int type, index;
+	int type, index = 0;
 
 	if (is_amd_pmu_msr(msr))
 		*emul = xen_amd_pmu_emulate(msr, val, is_read);