bump boot partition to 64Mb, as the kernel is getting fatter, fixes https://github.com/RobertCNelson/netinstall/issues/41

Signed-off-by: Robert Nelson <robertcnelson@gmail.com>

mk_mmc.sh

@@ -1272,7 +1272,7 @@ process_dtb_conf () {
 
 	#defaults, if not set...
 	conf_boot_startmb=${conf_boot_startmb:-"1"}
-	conf_boot_endmb=${conf_boot_endmb:-"48"}
+	conf_boot_endmb=${conf_boot_endmb:-"64"}
 	conf_root_device=${conf_root_device:-"/dev/mmcblk0"}
 
 	#error checking...