Description:kernelspace musl code

Team:OTHERS
Feature or Bugfix:Feature
Binary Source:NA
PrivateCode(Yes/No):No

Change-Id: I99874a7c570b7d22b4a3d34840260eb48ea3ffa1
Reviewed-on: http://mgit-tm.rnd.huawei.com/10276995Reviewed-by: Nshenwei 00579521 <denny.shenwei@huawei.com>
Tested-by: Npublic jenkins <public_jenkins@notesmail.huawei.com>

this is an obsolete error code from RFS, an obsolete predecessor of
NFS. POSIX documents it only as "Reserved", but maintains the
requirement that it be defined. as long as it is defined, it needs a
string for strerror to produce; the one chosen matches glibc and
documentation from other language runtimes I could find.

this definitely has the potential to be a bikeshed topic, so some
justification is in order. most of the changes made fit into one of
the following categories:
1. alignment with text in posix, xsh 2.3
2. eliminating overly-specific text for shared error codes
3. making the message match more closely with the macro name
4. removing extraneous words

in particular, the EAGAIN/EWOULDBLOCK text is updated to match the
description of EAGAIN (which covers both uses) rather than saying the
operation would block, and ENOTSUP/EOPNOTSUPP is updated not to
mention sockets.

the distinction between ENFILE/EMFILE has also been clarified; ENFILE
is aligned with the posix text, and EMFILE, which lacks concise posix
text matching any historic message, is updated to emphasize that the
exhausted resource is not open files/open file descriptions, but
rather the integer 'address space' of file descriptors.

some messages may be further tweaked based on feedback.