'drv_data->bitmap' is a bitmap. So use 'devm_bitmap_zalloc()' to simplify
code, improve the semantic.

This also fixes a spurious indentation.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/3ee83f75afa8754fade4fff6a03b57f0ae3ccc28.1640245993.git.christophe.jaillet@wanadoo.fr