pinctrl: renesas: checker: Validate drive strength configs consistency

Validate consistency of the pin control tables for pins with drive
strength capabilities.  If a pin has drive strength register bits
declarations in drive_regs[], the SH_PFC_PIN_CFG_DRIVE_STRENGTH flag
should be set in the pin's configs, and vice versa.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/0d5de01b5fe2c5fd23c3bea41077dc57ad105b9e.1640270559.git.geert+renesas@glider.be