rv: Fix __user specifier usage in extract_params()

rv: Fix __user specifier usage in extract_params()

The attributes variables extracted from syscalls in the helper are both
defined with the __user specifier although only the actual pointer to
user data should be marked.

Remove the __user specifier from attr.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202604150820.Ny143u6X-lkp@intel.com
Fixes: b133207deb72 ("rv: Add nomiss deadline monitor")
Reviewed-by: Wen Yang <wen.yang@linux.dev>
Reviewed-by: Nam Cao <namcao@linutronix.de>
Link: https://lore.kernel.org/r/20260601153840.124372-2-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>