powerpc/configs: Drop no longer needed CONFIG_DEVPTS_MULTIPLE_INSTANCES

Since commit eedf265a ("devpts: Make each mount of devpts an
independent filesystem.") we no longer need to set
CONFIG_DEVPTS_MULTIPLE_INSTANCES in our defconfigs.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/configs/powernv_defconfig

@@ -185,7 +185,6 @@ CONFIG_PPP_SYNC_TTY=m
 CONFIG_INPUT_EVDEV=m
 CONFIG_INPUT_MISC=y
 # CONFIG_SERIO_SERPORT is not set
-CONFIG_DEVPTS_MULTIPLE_INSTANCES=y
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_JSM=m

arch/powerpc/configs/pseries_defconfig

@@ -185,7 +185,6 @@ CONFIG_INPUT_EVDEV=m
 CONFIG_INPUT_MISC=y
 CONFIG_INPUT_PCSPKR=m
 # CONFIG_SERIO_SERPORT is not set
-CONFIG_DEVPTS_MULTIPLE_INSTANCES=y
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_ICOM=m