x86/sgx: Improve comments for sgx_encl_lookup/alloc_backing()

mainline inclusion
from mainline-v6.1-rc1
commit ee56a283
category: bugfix
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I6X1FF
CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ee56a283988d739c25d2d00ffb22707cb487ab47



Intel-SIG: commit ee56a283 x86/sgx: Improve comments for
sgx_encl_lookup/alloc_backing()
Incremental backporting patches for SGX on Intel Xeon platform.

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

Modify the comments for sgx_encl_lookup_backing() and for
sgx_encl_alloc_backing() to indicate that they take a reference
which must be dropped with a call to sgx_encl_put_backing().
Make sgx_encl_lookup_backing() static for now, and change the
name of sgx_encl_get_backing() to __sgx_encl_get_backing() to
make it more clear that sgx_encl_get_backing() is an internal
function.

Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/all/YtUs3MKLzFg+rqEV@zn.tnic/


[ Zhiquan: amend commit log. ]
Signed-off-by: Zhiquan Li <zhiquan1.li@intel.com>