drivers: nrfx: help select clock control when needed

CLOCK_CONTROL is required for fast instances of UART and COUNTER,
help select it when possible. The fast instances are UARTE120,
TIMER120 and TIMER121, and CLOCK_CONTROL is not supported for
CPUFLPR and CPUPPR even when the fast instances are used.

Signed-off-by: Bjarki Arge Andreasen <bjarki.andreasen@nordicsemi.no>