Thank you very much. I expanded the malloc into a bigger number and now I don't get those errors. My remaining problem is that I can't seem to move the serial console or console monitor (I don't know which term is better) into my flexcom1 usart. It always keep saying:
No serial driver found resetting ...
I followed the example that Nicolas pointed to (modified the stdout-path, modified the address, modified the pins, added the serial port into my device tree, modified all the CONFIGS in my defconfig file) but still I don't know why it doesn't link.
My device tree is alright because now I see that the drivers do get binded. If I disable the CONFIG_DEBUG_UART=n nothing gets displayed but if I activate it, it shows me the message above. Any idea on how to debug this help would be appreciated.