At present we assert:

  arm_el_is_aa64: Assertion `el >= 1 && el <= 3' failed.

The comment in arm_el_is_aa64 explains why asking about EL0 without
extra information is impossible.  Add an extra argument to provide
it from the surrounding context.

Fixes: 0ab5953bSigned-off-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20181008212205.17752-2-richard.henderson@linaro.org
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>