ARM: dts: msm: Add BT sleep clock configuration

Bluetooth requires external 32KHz sleep clock from PMD9635 in order
to operate at lower frequency clock thereby saving power during idle
scenarios.

CRs-Fixed: 749512
Change-Id: I363db15117404706007061c3e5b835f81d469c67
Signed-off-by: Anantha Krishnan <ananthk@codeaurora.org>