ARM: 6400/1: at91: fix arch_gettimeoffset fallout

ARM: 6400/1: at91: fix arch_gettimeoffset fallout

5cfc8ee0bb51 (ARM: convert arm to arch_gettimeoffset()) marked all of
at91 AND at91x40 as needing ARCH_USES_GETTIMEOFFSET, and hence no high
res timer support / accurate clock_gettime() - But only at91x40 needs it.

Cc: stable@kernel.org
Signed-off-by: Peter Korsgaard <peter.korsgaard@barco.com>
Acked-by: John Stultz <johnstul@us.ibm.com>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>