IncaIP is a SoC and its specific code should reside in an own
SoC subdirectory. Also add -mtune=4kc flag for CPU optimization.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@googlemail.com>
Cc: Wolfgang Denk <wd@denx.de>
Signed-off-by: Shinya Kuribayashi <skuribay@pobox.com>