ixp4xx: remove CONFIG_LEGACY_PTY from kernel config

Having legacy PTYs enabled causes problems with procd-hotplug.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

target/linux/ixp4xx/config-4.9

@@ -150,8 +150,6 @@ CONFIG_IXP4XX_WATCHDOG=y
 CONFIG_LEDS_FSG=y
 CONFIG_LEDS_GPIO=y
 CONFIG_LEDS_LATCH=y
-CONFIG_LEGACY_PTYS=y
-CONFIG_LEGACY_PTY_COUNT=256
 CONFIG_LZO_COMPRESS=y
 CONFIG_LZO_DECOMPRESS=y
 CONFIG_MACH_AP1000=y