platform/x86: fujitsu: clamp charge_control_end_threshold values to 50

Follow the sysfs ABI documentation that drivers should round written
values to the nearest supported value instead of returning an error.

Tested on a Fujitsu Lifebook U7720.

Signed-off-by: Jelle van der Waa <[e-mail]>
Reviewed-by: Hans de Goede <[e-mail]>
Acked-by: Jonathan Woithe <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Ilpo Järvinen <[e-mail]>
Signed-off-by: Ilpo Järvinen <[e-mail]>

drivers/platform/x86/fujitsu-laptop.c

···
 	if (ret)
 		return ret;
 
-	if (value < 50 || value > 100)
+	if (value > 100)
 		return -EINVAL;
+
+	if (value < 50)
+		value = 50;
 
 	cc_end_value = value * 0x100 + 0x20;
 	s006_cc_return = call_fext_func(fext, FUNC_S006_METHOD,