ARM: 6751/1: vexpress: select applicable errata workarounds in Kconfig

The Cortex-A9 tile on the Versatile Express suffers from a number of
engineering errata.

This patch selects workarounds in the ARCH_VEXPRESS_CA9X4 Kconfig entry
so that users don't need to worry about which ones to apply.

Reported-by: Ulrich Weigand <ulrich.weigand@de.ibm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>