h1r9: stop writing MAX2837 registers to MAX2839

h1r9: MAX2839 driver updates

h1r9: fix CLKOUT_EN pin setup

h1r9: use MAX2839

h1r9: implement additional MAX2839 functions, change some mreg definition names, fix RF gain control math

h1r9: add preliminary MAX2839 driver and accompanying header file; add some convenience macros to regs_def

h1r9: add preliminary MAX2839 register definitions

h1r9: bring-up wip

h1r9: add max2839_target.c

h1r9: add Si5351A support