hw/ppc/spapr_numa.c: simplify spapr_numa_write_assoc_lookup_arrays()

hw/ppc/spapr_numa.c: simplify spapr_numa_write_assoc_lookup_arrays()

We can get the job done in spapr_numa_write_assoc_lookup_arrays() a bit
cleaner:

- 'cur_index = int_buf = g_malloc0(..)' is doing a g_malloc0() in the
'int_buf' pointer and making 'cur_index' point to 'int_buf' all in a
single line. No problem with that, but splitting into 2 lines is clearer
to follow

- use g_autofree in 'int_buf' to avoid a g_free() call later on

- 'buf_len' is only being used to store the size of 'int_buf' malloc.
Remove the var and just use the value in g_malloc0() directly

- remove the 'ret' var and just return the result of fdt_setprop()

Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20220228175004.8862-12-danielhb413@gmail.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>