target-arm: Fix incorrect setting of E bit in CPSR

Commit 4cc3561 moved the exception mask bits out of env->uncached_cpsr
and into env->daif. However the env->daif contents are AArch64 style
mask bits, which include not just the AArch32 AIF bits but also the
new D bit (masks debug exceptions). This means that when reconstructing
the AArch32 CPSR value we must not allow the D bit in env->daif to get
into the CPSR, because the corresponding bit in the CPSR is E, the
endianness bit.

This bug didn't affect execution under TCG because we don't implement
endianness-swapping and so simply ignored the E bit; however it meant
that kernel booting under KVM failed, because KVM does honour the E bit.

Reported-by: Alexey Ignatov <lexszero@gmail.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target-arm/helper.c

@@ -2478,7 +2478,7 @@ uint32_t cpsr_read(CPUARMState *env)
         (env->CF << 29) | ((env->VF & 0x80000000) >> 3) | (env->QF << 27)
         | (env->thumb << 5) | ((env->condexec_bits & 3) << 25)
         | ((env->condexec_bits & 0xfc) << 8)
-        | (env->GE << 16) | env->daif;
+        | (env->GE << 16) | (env->daif & CPSR_AIF);
 }
 
 void cpsr_write(CPUARMState *env, uint32_t val, uint32_t mask)