qcom_tlmm: add initial gpio/pinmux controller (TLMM)

The qualcomm TLMM (top level mode manager) is their gpio/pinmux hardware
controller.

Although the pinmux is generic enough to use for the IPQ/APQ series
chips, I'm directly calling the IPQ4018 routines to expedite bring-up.

Notably, I'm not yet implementing the interrupt support - it's not
required at this stage of bring-up.

Differential Revision: https://reviews.freebsd.org/D33554