ARM: shmobile: r8a7779: Remove GENPD_FLAG_PM_CLK flag

The R-Car SYSC PM Domain only manages power domains for the main CPUs
and for coprocessors. It does not fill in the genpd .{at,de}tach_dev()
callbacks, and no power management clocks are registered for devices.
Hence pm_clk_{suspend,resume}() are no-ops, and setting of the
GENPD_FLAG_PM_CLK flag can be removed.

Originally the clock handling was copied from the R-Mobile PM Domain
code, which does manage a clock domain, in addition to device power
domains.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>