ARM: imx_v6_v7_defconfig: continue compiling the pwm driver

After the pwm-imx driver was split into two drivers and the Kconfig symbol
changed accordingly, use the new name to continue being able to use the
PWM hardware.
Signed-off-by: NUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm/configs/imx_v6_v7_defconfig

@@ -398,7 +398,7 @@ CONFIG_MAG3110=y
 CONFIG_MPL3115=y
 CONFIG_PWM=y
 CONFIG_PWM_FSL_FTM=y
-CONFIG_PWM_IMX=y
+CONFIG_PWM_IMX27=y
 CONFIG_NVMEM_IMX_OCOTP=y
 CONFIG_NVMEM_VF610_OCOTP=y
 CONFIG_TEE=y