ARM: 7502/1: contextidr: avoid using bfi instruction during notifier

The bfi instruction is not available on ARMv6, so instead use an and/orr
sequence in the contextidr_notifier. This gets rid of the assembler
error:

  Assembler messages:
  Error: selected processor does not support ARM mode `bfi r3,r2,#0,#8'

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>