msm: adsprpc: legacy devices don't need shared context bank

We are currently using shared context bank for attaching to sensors PD
though context banks are free as we have multiple use-cases (chre,drm)
on sensors PD but legacy devices don't have these use-cases so no need to
restrict to use shared context bank for attaching to sensors PD for legacy
devices.

Change-Id: I4c34da7d9029fd943fe8e40f79d41c1a0f40c380
Acked-by: Chenna Kesava Raju <chennak@qti.qualcomm.com>
Signed-off-by: Mohammed Nayeem Ur Rahman <mohara@codeaurora.org>