rpi-base.inc: Include modules if I2C is enaled

Add kernel modules i2c-dev and i2c-bcm2708 to variable
MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS if ENABLE_I2C is set to 1.
This affects images based on packagegroup-core-boot, including
the core-image-minimal image.

For other images (based on packagegroup-base) kernel modules
are provide through variable MACHINE_EXTRA_RRECOMMENDS.

Signed-off-by: Leon Anavi <leon.anavi@konsulko.com>

conf/machine/include/rpi-base.inc

@@ -76,7 +76,9 @@ MACHINE_FEATURES += "apm usbhost keyboard vfat ext2 screen touchscreen alsa blue
 # Raspberry Pi has no hardware clock
 MACHINE_FEATURES_BACKFILL_CONSIDERED = "rtc"
 
-MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS += " kernel-modules udev-rules-rpi"
+MACHINE_EXTRA_RRECOMMENDS += "kernel-modules udev-rules-rpi"
+MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS += "${@oe.utils.conditional('ENABLE_I2C', '1', 'kernel-module-i2c-dev kernel-module-i2c-bcm2708', '', d)}"
+
 
 # Set Raspberrypi splash image
 SPLASH = "psplash-raspberrypi"