raid1: Add some macros to make code clearly.
raid1: Add some macros to make code clearly.

In a subsequent patch, we'll use some const parameters.
Using macros will make the code clearly.

Signed-off-by: Jianpeng Ma <c2efc80ba27cf31d4676f82b7232757b76911f7a@gmail.com>
Signed-off-by: NeilBrown <1c00aa603bb92d594c03cff60ecf8e63b2a5bcb1@suse.de>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs