Kconfig: add avtimer config for trinket

Avtimer driver is used by camera to get
timestamp from ADSP on trinket. Add
required config so to enable it in defconfig.

Change-Id: Ida097b0eb125f395ed7b34db0ad67a72ebdb5091
Signed-off-by: Laxminath Kasam <lkasam@codeaurora.org>