target-i386: Use 1UL for bit shift

Fix undefined behavior detected by clang runtime check:

  qemu/target-i386/cpu.c:1494:15: runtime error:
    left shift of 1 by 31 places cannot be represented in type 'int'

While doing that, add extra parenthesis for clarity.

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index c92dd06..c1a9e09 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -1491,7 +1491,7 @@
     int i;
 
     for (i = 0; i < 32; ++i) {
-        if (1 << i & mask) {
+        if ((1UL << i) & mask) {
             const char *reg = get_register_name_32(f->cpuid_reg);
             assert(reg);
             fprintf(stderr, "warning: %s doesn't support requested feature: "