target-tricore: fix depositing bits from PCXI into ICR

Spotted by Coverity, because (env->PCXI & MASK_PCXI_PCPN) >> 24
is always zero.  The immediately preceding assignment is also
wrong though.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Message-Id: <1435147270-1040-1-git-send-email-pbonzini@redhat.com>