x86/sgx: Add wrapper for SGX2 EAUG function

Add a wrapper for the EAUG ENCLS leaf function used to
add a page to an initialized enclave.

EAUG:
1) Stores all properties of the new enclave page in the SGX
   hardware's Enclave Page Cache Map (EPCM).
2) Sets the PENDING bit in the EPCM entry of the enclave page.
   This bit is cleared by the enclave by invoking ENCLU leaf
   function EACCEPT or EACCEPTCOPY.

Access from within the enclave to the new enclave page is not
possible until the PENDING bit is cleared.
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lkml.kernel.org/r/97a46754fe4764e908651df63694fb760f783d6e.1652137848.git.reinette.chatre@intel.com

arch/x86/kernel/cpu/sgx/encls.h

@@ -227,4 +227,10 @@ static inline int __emodt(struct sgx_secinfo *secinfo, void *addr)
 	return __encls_ret_2(EMODT, secinfo, addr);
 }
 
+/* Zero a page of EPC memory and add it to an initialized enclave. */
+static inline int __eaug(struct sgx_pageinfo *pginfo, void *addr)
+{
+	return __encls_2(EAUG, pginfo, addr);
+}
+
 #endif /* _X86_ENCLS_H */