clk: renesas: cpg-mssr: propagate return value of_genpd_add_provider_simple()

clk: renesas: cpg-mssr: propagate return value of_genpd_add_provider_simple()

of_genpd_add_provider_simple() might fail, this patch makes sure we check
the return value of of_genpd_add_provider_simple() by propagating the
return value to the caller of cpg_mssr_add_clk_domain().

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://lore.kernel.org/r/20211117115101.28281-5-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>