selftests/sgx: Test two different SGX2 EAUG flows

Enclave pages can be added to an initialized enclave when an address
belonging to the enclave but without a backing page is accessed from
within the enclave.

Accessing memory without a backing enclave page from within an enclave
can be in different ways:
1) Pre-emptively run ENCLU[EACCEPT]. Since the addition of a page
   always needs to be accepted by the enclave via ENCLU[EACCEPT] this
   flow is efficient since the first execution of ENCLU[EACCEPT]
   triggers the addition of the page and when execution returns to the
   same instruction the second execution would be successful as an
   acceptance of the page.

2) A direct read or write. The flow where a direct read or write
   triggers the page addition execution cannot resume from the
   instruction (read/write) that triggered the fault but instead
   the enclave needs to be entered at a different entry point to
   run needed ENCLU[EACCEPT] before execution can return to the
   original entry point and the read/write instruction that faulted.

Add tests for both flows.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lkml.kernel.org/r/0c321e0e32790ac1de742ce5017a331e6d902ac1.1652137848.git.reinette.chatre@intel.com