Set sysclk before using it

Set sysclk before using it

simpleaudio_set_params() calls set_params() which reads sysclk off the
"i2s_clk" property before it sets that very clock's rate with
dd_set_sysclk() (in case there's multiplier specified).

Hence reverse the order so set_params() can pick up the newly set rate.

The rate is still off on the Pinebook Pro, but I came across this when
reading the code;  this also matches NetBSD's sys/dev/fdt/ausoc.c r1.6
"Set sysclk rate at set_format time, so the link set_format callback can
read the new sysclk".

OK kettenis patrick