mtd: integck needs MMU support

After fixing build issue related to MS_DIRSYNC and MS_RELATIME, we get
following build error with blackfin external toolchain.

fstest_monitor.c: In function 'main':
fstest_monitor.c:237: warning: implicit declaration of function 'fork'
/tmp/ccCzZIuW.o: In function 'main':
/home/rahul.bedarkar/buildroot/output/build/mtd-1.5.2/tests/fs-tests/utils/fstest_monitor.c:237: undefined reference to '_fork'
collect2: ld returned 1 exit status
make[2]: *** [fstest_monitor] Error 1

Since it uses fork(), add dependency on MMU support for integck.

Signed-off-by: Rahul Bedarkar <rahul.bedarkar@imgtec.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>