x86/sgx: Drop 'page_index' from sgx_backing

mainline inclusion
from mainline-6.0-rc1
commit e0a5915f
category: feature
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I5USAM


CVE: NA

Intel-SIG: commit e0a5915f x86/sgx: Drop 'page_index' from
sgx_backing.
Backport for SGX EDMM support.

--------------------------------

Storing the 'page_index' value in the sgx_backing struct is
dead code and no longer needed.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/20220708162124.8442-1-kristen@linux.intel.com


Signed-off-by: Zhiquan Li <zhiquan1.li@intel.com>