megasas: remove buildtime strings

Using __DATE__ or __TIME__ in binary pkgs changes the checksum of
compiled binaries if they get rebuilt, even if there are no other
source changes.  Replace the dynamic strings with some equally
informative static strings.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>