Fix serial flow control on Si1060 radios

[povik]

Add missing control pin definitions for ISM01A and missing pin initialization for all Si1060 radios.

I can vouch for this being the right thing on ISM01A, I assume this must be right for the other Si1060 radios as well but it would be best if someone with access to schematics would okay it.

Cc: @gumerrgz