CVE-2024-39461: clk: bcm: rpi: Assign ->num before accessing ->hws

In the Linux kernel, the following vulnerability has been resolved:

clk: bcm: rpi: Assign ->num before accessing ->hws

Commit f316cdff8d67 ("clk: Annotate struct clkhwonecelldata with countedby") annotated the hws member of 'struct clkhwonecelldata' with countedby, which informs the bounds sanitizer about the number of elements in hws, so that it can warn when hws is accessed out of bounds. As noted in that change, the countedby member must be initialized with the number of elements before the first array access happens, otherwise there will be a warning from each access prior to the initialization because the number of elements is zero. This occurs in raspberrypidiscoverclocks() due to ->num being assigned after ->hws has been accessed:

UBSAN: array-index-out-of-bounds in drivers/clk/bcm/clk-raspberrypi.c:374:4 index 3 is out of range for type 'struct clkhw [] countedby(num)' (aka 'struct clkhw []')

Move the ->num initialization to before the first access of ->hws, which clears up the warning.