checkpatch: update $declaration_macros, add uninitialized_var

Using uninitialized_var reports a false positive for "Missing blank line
after declarations".

Fix it by adding uninitialized_var to the $declaration_macros exceptions
list.

Move the macro list after $Type is declared.

Add optional prefixes to DECLARE_<FOO> and DEFINE_<BAR>
macro declarations to allow forms like:
	MLX4_DECLARE_DOORBELL_LOCK

Signed-off-by: Joe Perches <joe@perches.com>
Reported-by: Dotan Barak <dotanb@mellanox.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>