arm64: enable HAVE_IRQ_TIME_ACCOUNTING for arm64

The only dependency for irq time accounting is a sufficiently high
resolution timer. Plenty of arm64 platforms will have this, so enable
this feature.

Change-Id: Id675a541a6813a14ae0b7e1bb66670bf7467a97f
Signed-off-by: Steve Muckle <smuckle@codeaurora.org>