sim: bfin: fix build warnings w/newer gcc

The bfin_otp_write_page_val func wants a pointer to an bu64[2] array,
but this code passes it a pointer to a single bu64.  It's in a struct
with a known compatible layout:
	bu64 data0, data1, data2, data3;
But gcc doesn't allow these kinds of tricks anymore.  Use the more
verbose form to make the compiler happy since this is not performance
sensitive code.