package/libexif: security bump to version 0.6.22

package/libexif: security bump to version 0.6.22

- Switch site to github
- Drop patches (already in version)
- Fix the following CVEs:
  - CVE-2020-13114: Time consumption DoS when parsing canon array
    markers
  - CVE-2020-13113: Potential use of uninitialized memory
  - CVE-2020-13112: Various buffer overread fixes due to integer
    overflows in maker notes
  - CVE-2020-0093: read overflow
  - CVE-2020-12767: fixed division by zero

https://github.com/libexif/libexif/releases/tag/libexif-0_6_22-release

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>