nfp: flower: use vmalloc_array() to simplify code

nfp: flower: use vmalloc_array() to simplify code

Remove array_size() calls and replace vmalloc() with vmalloc_array() in
nfp_flower_metadata_init().  vmalloc_array() is also optimized better,
resulting in less instructions being used.

Place 'NFP_FL_STATS_ELEM_RS' with the sizeof() parameter as the second
argument to vmalloc_array() to avoid -Wcalloc-transposed-args compilation
warnings.

Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>
Link: https://patch.msgid.link/20250816090659.117699-3-rongqianfeng@vivo.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>