ARMv8.5 MTE: Add MTE compatible version of strchr.

Reading outside the range of the string is only allowed within 16 byte
aligned granules when MTE is enabled.

This implementation is based on string/aarch64/strchr.S

The 64-bit syndrome value is changed to contain only 16 bytes of
data.
The 32 byte loop is unrolled by two 16 byte reads.
3 files changed