xen/arm: Update the ASSERT() in SYNCHRONIZE_SERROR()

xen/arm: Update the ASSERT() in SYNCHRONIZE_SERROR()

The macro SYNCHRONIZE_SERROR() has an assert to check whether it will
be called with Abort interrupt unmasked. However, this is only done if
a given cap is not enabled.

None of the callers will treat the abort interrupt differently
depending on a feature. Furthermore, it makes more difficult to check
whether SYNCHRONIZE_SERROR() is going to be called with abort interrupt
unmasked.

Therefore, we now require the abort interrupt to be unmasked regardless
the state of the cap.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Release-acked-by: Juergen Gross <jgross@suse.com>