[ARM] Feroceon: support old cores with ARM926 ID

This enables the usage of some old Feroceon cores
for which the CPU ID is equal to the ARM926 ID.
Relevant for Feroceon-1850 and old Feroceon-2850.

Signed-off-by: Tzachi Perelstein <tzachi@marvell.com>
Signed-off-by: Nicolas Pitre <nico@marvell.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>