gpio: samsung: Update documentation

hardware.h inclusion is no longer needed. Update the documentation section
related to it and fix a file path.
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/arm/Samsung-S3C24XX/GPIO.txt

@@ -85,21 +85,10 @@ between the calls.
 Headers
 -------
 
-  See arch/arm/mach-s3c2410/include/mach/regs-gpio.h for the list
+  See arch/arm/mach-s3c24xx/include/mach/regs-gpio.h for the list
   of GPIO pins, and the configuration values for them. This
   is included by using #include <mach/regs-gpio.h>
 
-  The GPIO management functions are defined in the hardware
-  header arch/arm/mach-s3c2410/include/mach/hardware.h which can be
-  included by #include <mach/hardware.h>
-
-  A useful amount of documentation can be found in the hardware
-  header on how the GPIO functions (and others) work.
-
-  Whilst a number of these functions do make some checks on what
-  is passed to them, for speed of use, they may not always ensure
-  that the user supplied data to them is correct.
-
 
 PIN Numbers
 -----------