lmb: replace the double-underscore with single-underscore for all functions

lmb: replace the double-underscore with single-underscore for all functions

A bunch of static functions in the LMB module have used a
double-undersore for the function names. It was suggested to use a
single-underscore instead, as the double-underscore is usually used
by library functions. Replace the double-underscore with
single-underscore for all functions.

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Suggested-by: Simon Glass <sjg@chromium.org>