soc: ti: k3-ringacc: Use devm_bitmap_zalloc() when applicable

'rings_inuse' and 'proxy_inuse' are bitmaps. So use 'devm_bitmap_zalloc()'
to simplify code and improve the semantic.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Nishanth Menon <nm@ti.com>
Link: https://lore.kernel.org/r/45544b0d97a7bea7764292852842adf5085a7700.1640276001.git.christophe.jaillet@wanadoo.fr