pinctrl: sh-pfc: Do not unconditionally support PIN_CONFIG_BIAS_DISABLE

Always stating PIN_CONFIG_BIAS_DISABLE is supported gives untrue output
when examining /sys/kernel/debug/pinctrl/e6060000.pfc/pinconf-pins if
the operation get_bias() is implemented but the pin is not handled by
the get_bias() implementation. In that case the output will state that
"input bias disabled" indicating that this pin has bias control
support.

Make support for PIN_CONFIG_BIAS_DISABLE depend on that the pin either
supports SH_PFC_PIN_CFG_PULL_UP or SH_PFC_PIN_CFG_PULL_DOWN. This also
solves the issue where SoC specific implementations print error messages
if their particular implementation of {set,get}_bias() is called with a
pin it does not know about.

Signed-off-by: Niklas Söderlund <[e-mail]>
Acked-by: Laurent Pinchart <[e-mail]>
Signed-off-by: Geert Uytterhoeven <[e-mail]>

drivers/pinctrl/sh-pfc/pinctrl.c

···
 
 	switch (param) {
 	case PIN_CONFIG_BIAS_DISABLE:
-		return true;
+		return pin->configs &
+			(SH_PFC_PIN_CFG_PULL_UP | SH_PFC_PIN_CFG_PULL_DOWN);
 
 	case PIN_CONFIG_BIAS_PULL_UP:
 		return pin->configs & SH_PFC_PIN_CFG_PULL_UP;