iio: sx9310: Fix semtech,avg-pos-strength setting when > 16

This DT property can be 0, 16, and then 64, but not 32. The math here
doesn't recognize this slight bump in the power of 2 numbers and
translates a DT property of 64 into the register value '3' when it
really should be '2'. Fix it by subtracting one more if the number being
translated is larger than 31. Also use clamp() because we're here.

Cc: Daniel Campello <[email protected]>
Cc: Lars-Peter Clausen <[email protected]>
Cc: Peter Meerwald-Stadler <[email protected]>
Cc: Douglas Anderson <[email protected]>
Cc: Gwendal Grignou <[email protected]>
Cc: Evan Green <[email protected]>
Signed-off-by: Stephen Boyd <[email protected]>
Reviewed-by: Douglas Anderson <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jonathan Cameron <[email protected]>

drivers/iio/proximity/sx9310.c

@@ -1305,7 +1305,8 @@ sx9310_get_default_reg(struct sx9310_data *data, int i,
 		if (ret)
 			break;
 
-		pos = min(max(ilog2(pos), 3), 10) - 3;
+		/* Powers of 2, except for a gap between 16 and 64 */
+		pos = clamp(ilog2(pos), 3, 11) - (pos >= 32 ? 4 : 3);
 		reg_def->def &= ~SX9310_REG_PROX_CTRL7_AVGPOSFILT_MASK;
 		reg_def->def |= FIELD_PREP(SX9310_REG_PROX_CTRL7_AVGPOSFILT_MASK,
 					   pos);