um: Remove unused asm/archparam.h header

This header is no longer used after the removal of fixmap support
in commit 5bfc4a3 ("um: Remove obsolete fixmap support").

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20250113153218.3331321-3-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Author: btw616