target-ppc: Store Quadword Conditional Drops Size Bit

The size and register information are encoded into the reserve_info field
of CPU state in the store conditional translation code.  Specifically, the
size is shifted left by 5 bits (see target-ppc/translate.c gen_conditional_store).

The user-mode store conditional code erroneously extracts the size by ANDing
with a 4 bit mask; this breaks if size >= 16.

Eliminate the mask to make the extraction of size mirror its encoding.
Signed-off-by: NTom Musta <tommusta@gmail.com>
Signed-off-by: NAlexander Graf <agraf@suse.de>

linux-user/main.c

@@ -1497,7 +1497,7 @@ static int do_store_exclusive(CPUPPCState *env)
         segv = 1;
     } else {
         int reg = env->reserve_info & 0x1f;
-        int size = (env->reserve_info >> 5) & 0xf;
+        int size = env->reserve_info >> 5;
         int stored = 0;
 
         if (addr == env->reserve_addr) {