ARM: fix booting low-vectors machines

ARM: fix booting low-vectors machines

commit d8aa712c30148ba26fd89a5dc14de95d4c375184 upstream.

Commit f6f91b0d9fd9 (ARM: allow kuser helpers to be removed from the
vector page) required two pages for the vectors code.  Although the
code setting up the initial page tables was updated, the code which
allocates page tables for new processes wasn't, neither was the code
which tears down the mappings.  Fix this.

Fixes: f6f91b0d9fd9 ("ARM: allow kuser helpers to be removed from the vector page")
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>