mips: vocore2: fix various issues

- fix SPL image generation
- fix incorrect console output
- increase malloc_f and malloc_r space to fix LZMA decompression errors
- increase SPI flash clock

Signed-off-by: Mauro Condarelli <mc5686@mclink.it>
[squashed to one patch, fix commit subject and description]
Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>