x86: avoid AREG0 for exceptions

x86: avoid AREG0 for exceptions

Add an explicit CPUX86State parameter instead of relying on AREG0.

Merge raise_exception_env() to raise_exception(), likewise with
raise_exception_err_env() and raise_exception_err().

Introduce cpu_svm_check_intercept_param() and cpu_vmexit()
as wrappers.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>