arm:trats: Increase malloc pool size (for DFU ext4 transfers)

Commit:
dfu: make data buffer size configurable
SHA1: 89a72b2e0e141042c9109185e02d39b2107ffc62

replaced statically allocated buffers with one allocated with memalign.

Malloc pool size of 1MiB was too small, since we needed bigger buffer to
transfer for example uImage.

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Cc: Minkyu Kang <mk7.kang@samsung.com>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>