staging: lustre: Remove DECLARE_LU_VARS macro

This macro was only used in four places to declare two variables.
It saved one line of code, but in our opinion hurt readability.
So we removed the macro, substituting every occurrence with the
declaration of the two variables (like the preprocessor would have done).

Signed-off-by: Fabian Huegel <fabian_huegel@web.de>
Signed-off-by: Christoph Volkert <linux@christoph-volkert.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>