[libc][errno] Remove non asm generic error number (#92172)

The following small thing caught my eye:

1) `EILSEQ` is not part of the generic asm error number macros. See the
[full list of generic asm errno
codes](https://github.com/torvalds/linux/blob/4b95dc87362aa57bdd0dcbad109ca5e5ef3cbb6c/include/uapi/asm-generic/errno-base.h).
AFAIK the generic asm errno numbers are common between different
operating systems and architectures. `EILSEQ` is not part of this common
set of errno's.

2) `EILSEQ`'s value is wrong. During the addition of `EILSEQ` in
https://reviews.llvm.org/D151129, the value `35` was probably chosen as
its the consecutive number. This is not correct. The actual values can
be looked up for example here:
* [For Linux
kernel](https://github.com/search?q=repo%3Atorvalds%2Flinux+EILSEQ&type=code&p=1):
`EILSEQ = 84` (uapi; i.e. x86_64), `EILSEQ = 88` (mips), `EILSEQ = 47`
(parisc)
* [For Darwin
kernel](https://github.com/apple-oss-distributions/xnu/blob/main/bsd/sys/errno.h#L237):
`EILSEQ = 92`