regex/octeontx2: fix driver name

regex/octeontx2: fix driver name

Following the recent alignment of all driver names,
this new driver get unaligned:
	librte_regex_octeontx2_regex.so

The 'fmt_name' must be "octeontx2_regex", and if not provided,
is taken from the 'name' variable.
But the variable 'name' should not be overwritten,
to keep the automatic value from the directory name.

The library name will be composed of the class directory
and the driver directory name:
	librte_regex_octeontx2.so

Reported-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: David Marchand <david.marchand@redhat.com>