arm: mx6: novena: Define CONFIG_SYS_MALLOC_F_LEN

arm: mx6: novena: Define CONFIG_SYS_MALLOC_F_LEN

This board uses setup_i2c() in SPL. The setup_i2c() function internally
calls gpio_request(), which in turn internally calls strdup(). The strdup()
requires a running mallocator, so this patch makes the mallocator available.

Signed-off-by: Marek Vasut <[email protected]>
Cc: Igor Grinberg <[email protected]>
Cc: Nikita Kiryanov <[email protected]>
Cc: Sean Cross <[email protected]>
Cc: Simon Glass <[email protected]>
Cc: Stefano Babic <[email protected]>
Cc: Tim Harvey <[email protected]>