migration/qemu-file.c: Don't shift left into sign bit

Add a cast in qemu_get_be32() to avoid shifting left into the sign
bit of a signed integer (which is undefined behaviour in C).
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

migration/qemu-file.c

@@ -503,7 +503,7 @@ unsigned int qemu_get_be16(QEMUFile *f)
 unsigned int qemu_get_be32(QEMUFile *f)
 {
     unsigned int v;
-    v = qemu_get_byte(f) << 24;
+    v = (unsigned int)qemu_get_byte(f) << 24;
     v |= qemu_get_byte(f) << 16;
     v |= qemu_get_byte(f) << 8;
     v |= qemu_get_byte(f);