lmb: remove lmb_is_nomap() from include

Defining static functions in includes should be avoided.
Function lmb_is_nomap() is only used in the unit test.
So move it to the unit test.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>