git: bump version to 2.6.4

- Bump version to 2.6.4
- Update the hash value
- Remove 0002-Makefile-make-curl-config-path-configurable.patch
  - This patch is now part of upstream:
    https://github.com/git/git/commit/f89158760d5f02ba59f644799abd921e6be22f13



Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>