meta-flow: Remove duplicate break statements.

Commit 8bfd0fda mistakenly introduced duplicate "break;" statements to
MFF_MPLS_BOS handling. This patch removes them.

Found by inspection.

Signed-off-by: Joe Stringer <joestringer@nicira.com>
Acked-by: Jarno Rajahalme <jrajahalme@nicira.com>
Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
INSTALL: Mention that building a kernel module is optional.

It used to be essentially required, but now it's reasonable to use the
kernel's builtin module.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Reviewed-by: Flavio Leitner <fbl@redhat.com>