utils/genrandconfig: fix ext2 config variable

This should have been BR2_TARGET_ROOTFS_EXT2 as the
BR2_TARGET_ROOTFS_EXT2_GEN variable is an integer variable used
to indicate the ext2/ext3/ext4 variant.

Fixes:
 - http://autobuild.buildroot.net/results/5d7/5d7833212bd8a2b575945f848d8c91dabe7d3c30

Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

utils/genrandconfig

@@ -443,7 +443,7 @@ def fixup_config(sysinfo, configfile):
         configlines.remove('BR2_TARGET_OPTEE_OS=y\n')
         configlines.remove('BR2_TARGET_OPTEE_OS_PLATFORM=""\n')
 
-    if 'BR2_TARGET_ROOTFS_EXT2_GEN=y\n' in configlines and \
+    if 'BR2_TARGET_ROOTFS_EXT2=y\n' in configlines and \
        'BR2_TARGET_ROOTFS_EXT2_SIZE="60M"\n' in configlines:
         configlines.remove('BR2_TARGET_ROOTFS_EXT2_SIZE="60M"\n')
         configlines.append('BR2_TARGET_ROOTFS_EXT2_SIZE="%s"\n' % ROOTFS_SIZE)