at91sam4: Add missing SAM4S family CHIPIDs and remove FWS=6.

Add missing CHIPID values for all SAM4S parts listed in revision K of
Atmel-11100-32-bit Cortex-M4-Microcontroller-SAM4S_Datasheet.pdf. I have
also removed the FWS=6 workaround, as this appears to be a copy-paste error
from the SAM3X family.

Change-Id: I1ce1d82911f39d6fcb8f04034f5c9c9bf2818466
Signed-off-by: Owen Kirby <oskirby@gmail.com>
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: http://openocd.zylin.com/3837
Tested-by: jenkins