clk: renesas: cpg-mssr: Remove unused [RM]MSTPCR() definitions

The Realtime Module Stop Control Register definitions (RMSTPCR(i)) are
incorrect for i >= 8 on R-Car Gen2 and Gen3.

As these are unused, and not planned to be used, just like the
corresponding Modem Module Stop Control Register definitions (MMSTPCR())
on R-Mobile APE6 (they are intended for the software running on the
Real-Time and Modem CPU cores), they can just be removed.

Reported-by: Hai Nguyen Pham <hai.pham.ud@renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/2d8bc4d9806b419ebb06030d2f31b2ea1e59b1d6.1620119700.git.geert+renesas@glider.be