soc: sunxi: SUN20I_PPU should depend on PM

soc: sunxi: SUN20I_PPU should depend on PM

An $ARCH or a platform should select PM. Single device drivers
should only depend on PM, not select it.

Having SUN20I_PPU depend on PM removes a kconfig warning:

WARNING: unmet direct dependencies detected for PM
  Depends on [n]: !MMU [=y]
  Selected by [y]:
  - SUN20I_PPU [=y] && (ARCH_SUNXI || COMPILE_TEST [=y])

Fixes: 0ad2185dcb5e ("soc: sunxi: select CONFIG_PM")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Jernej Skrabec <jernej.skrabec@gmail.com>
Cc: Samuel Holland <samuel@sholland.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-sunxi@lists.linux.dev
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>