target-i386: correctly propagate retaddr into SVM helpers

Commit 2afbdf84 ("target-i386: exception handling for memory helpers",
2015-09-15) changed tlb_fill's cpu_restore_state+raise_exception_err
to raise_exception_err_ra.  After this change, the cpu_restore_state
and raise_exception_err's cpu_loop_exit are merged into
raise_exception_err_ra's cpu_loop_exit_restore.

This actually fixed some bugs, but when SVM is enabled there is a
second path from raise_exception_err_ra to cpu_loop_exit.  This is
the VMEXIT path, and now cpu_vmexit is called without a
cpu_restore_state before.

The fix is to pass the retaddr to cpu_vmexit (via
cpu_svm_check_intercept_param).  All helpers can now use GETPC() to pass
the correct retaddr, too.

Cc: qemu-stable@nongnu.org
Fixes: 2afbdf84
Reported-by: Alexander Boettcher <alexander.boettcher@genode-labs.com>
Tested-by: Alexander Boettcher <alexander.boettcher@genode-labs.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>