ARM: 6387/1: errata: check primary part ID in proc-v7.S

Kconfig doesn't have any knowledge of specific v7 cores, so it is possible
to select errata workarounds that may cause inadvertent behaviour when
executed on a core other than those targetted by the fix.

This patch improves the variant and revision checking in proc-v7.S so
that the primary part number is also considered when applying errata
workarounds.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>