hw/pxa2xx.c: Fix handling of R/WC bits in PMCR

Fix a bug in handling the write-one-to-clear bits in the PMCR
which meant that we would always clear the bit even if the
value written was a zero. Spotted by Coverity (see bug 887883).
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/pxa2xx.c

@@ -114,7 +114,9 @@ static void pxa2xx_pm_write(void *opaque, target_phys_addr_t addr,
 
     switch (addr) {
     case PMCR:
-        s->pm_regs[addr >> 2] &= 0x15 & ~(value & 0x2a);
+        /* Clear the write-one-to-clear bits... */
+        s->pm_regs[addr >> 2] &= ~(value & 0x2a);
+        /* ...and set the plain r/w bits */
         s->pm_regs[addr >> 2] |= value & 0x15;
         break;