overclock: remove cpu frequency 1804 MHz

* if enable overclock to 1804 MHz will cause the phone freezing

This fix it.
fixed O3 optimize not booting when compile with linaro 4.8.1

* Fix by added -fno-inline-functions to O3 optimization.

Thanks Christopher83 for hint.
defconfig: use O3 optimization
Makefile: added optimization check for module
skull kernel v1.4.1