[uaccess] Remove user_to_phys() and phys_to_user()

Remove the intermediate concept of a user pointer from physical
address conversions, leaving virt_to_phys() and phys_to_virt() as the
directly implemented functions.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/interface/linux/linux_uaccess.c

@@ -27,6 +27,7 @@ FILE_LICENCE(GPL2_OR_LATER);
  *
  */
 
-PROVIDE_UACCESS_INLINE(linux, user_to_phys);
+PROVIDE_UACCESS_INLINE(linux, phys_to_virt);
+PROVIDE_UACCESS_INLINE(linux, virt_to_phys);
 PROVIDE_UACCESS_INLINE(linux, virt_to_user);
 PROVIDE_UACCESS_INLINE(linux, memchr_user);