xtensa: get rid uapi/asm/param.h

The only difference between it and generic is the stray (and utterly
useless) definition of NGROUPS.  It had been removed on all architectures
back in 2004; xtensa port began prior to that and hadn't been merged
until 2005, so it had missed the purge.

Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Author: Al Viro