sam3: Merge sam4e8e support into sam3 code

Most of the peripherals on the sam4e8e are similar to the ones on the
sam3x8e mcu.  Merge the code together and use just one code directory.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/Kconfig

@@ -6,12 +6,10 @@ choice
     prompt "Micro-controller Architecture"
     config MACH_AVR
         bool "Atmega AVR"
-    config MACH_SAM3X8E
-        bool "SAM3x8e (Arduino Due)"
+    config MACH_SAM3
+        bool "SAM3/SAM4 (Due and Duet)"
     config MACH_SAMD21
         bool "SAMD21 (Arduino Zero)"
-    config MACH_SAM4E8E
-        bool "SAM4e8e (Duet Wifi/Eth)"
     config MACH_LPC176X
         bool "LPC176x (Smoothieboard)"
     config MACH_STM32F1
@@ -27,7 +25,6 @@ endchoice
 source "src/avr/Kconfig"
 source "src/sam3/Kconfig"
 source "src/samd21/Kconfig"
-source "src/sam4e8e/Kconfig"
 source "src/lpc176x/Kconfig"
 source "src/stm32f1/Kconfig"
 source "src/pru/Kconfig"