bcm2835-bootloader: create flash/sdcard optimized ext4 filesystem

See http://blogofterje.wordpress.com/2012/01/14/optimizing-fs-on-sd-card/ for
reference:
- disable journaling
- set stride and stripe-width
- set block size to 4k
bcm2835-bootloader create_sdcard: create the storage partition aligned on 4mb
Merge pull request #3021 from steeve/optimize_flash

Optimize SD card partitioning and formatting for SD/Flash