rmnet_shs: Fix invalid init for disabled RPS

Previously if rmnet_shs was initialized when
RPS mask was invalid it would cause a invalid
partial initialization.

This changes fixes that condition and allows
rmnet_shs to handle an invalid RPS mask correctly.

CRs-Fixed: 2465433
Change-Id: Idc6a92af582ccd390d57ed89f708a5f53593a86e
Acked-by: Raul Martinez <mraul@qti.qualcomm.com>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>