Note, beside this, to make driver workable, this patch:

- changes SRAM memory distribution. Actually, we have 128K in STM (as
opposite to 64K in A2F). TBDs here: a) CONFIG_MEM_RAM_LEN is a bad
name, since this isn't length of full SRAM, but just a part of it; b)
we should control the summary length of MEM_xxx areas somehow, on a
SOC basis (i.e. A2F has 64K SRAM, STM32F2 has 128K SRAM, etc.), maybe
include/configs/cortex-m3-common.h would be the best choice; c) not
sure if we want to have *all* SRAM parts configurable, e.g. MALLOC size
may be determined automatically.

- in default configuration load files to SRAM (RAM_BUF) (as opposite
to external RAM). TBD here: make this configurable somehow.

Signed-off-by: Yuri Tikhonov <yur@emcraft.com>