nimble/phy/cmac: Use 31250 tps timer
nimble/phy/cmac: Use 31250 tps timer

This adjusts phy to 31250 tps timer used in LL on CMAC.

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble