ARM: s3c24xx: use new PWM driver

The samsung PWM driver has moved to the new PWM subsystem, which
changed the Kconfig symbol for that driver, but the rx1950 and
gta02 boards still uses the old one.

Without this patch, building s3c2410_defconfig results in:

arch/arm/mach-s3c24xx/built-in.o: In function `rx1950_lcd_power':
arch/arm/mach-s3c24xx/mach-rx1950.c:430: undefined reference to `pwm_config'
arch/arm/mach-s3c24xx/mach-rx1950.c:431: undefined reference to `pwm_disable'
arch/arm/mach-s3c24xx/mach-rx1950.c:437: undefined reference to `pwm_config'
arch/arm/mach-s3c24xx/mach-rx1950.c:438: undefined reference to `pwm_enable'
arch/arm/mach-s3c24xx/built-in.o: In function `rx1950_backlight_exit':
arch/arm/mach-s3c24xx/mach-rx1950.c:504: undefined reference to `pwm_free'
arch/arm/mach-s3c24xx/built-in.o: In function `rx1950_backlight_init':
arch/arm/mach-s3c24xx/mach-rx1950.c:487: undefined reference to `pwm_request'

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reported-by: Tushar Behera <tushar.behera@linaro.org>
Cc: Kukjin Kim <kgene.kim@samsung.com>