clk: renesas: cpg-mssr: Migrate to CLK_IS_CRITICAL

When the Renesas CPG/MSSR driver was introduced, it was anticipated that
critical clocks would be handled through a new CLK_ENABLE_HAND_OFF flag
soon.  However, CLK_ENABLE_HAND_OFF never made it upstream.

Instead, commit 32b9b109 ("clk: Allow clocks to be marked as
CRITICAL") introduced CLK_IS_CRITICAL, a flag with slightly differing
semantics.  Still, it can be used to prevent e.g. the GIC module clock
from being turned off, until the GIC-400 driver has full support for
Runtime PM.

Hence migrate the Renesas CPG/MSSR driver from CLK_ENABLE_HAND_OFF to
CLK_IS_CRITICAL.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>