tiff: bump version to 4.0.8

tiff: bump version to 4.0.8

Patch 0001 already included in this release:
  https://github.com/vadz/libtiff/commit/438274f938e046d33cb0e1230b41da32ffe223e1

Patch 0002 already included in this release:
  https://github.com/vadz/libtiff/commit/43bc256d8ae44b92d2734a3c5bc73957a4d7c1ec

Patch 0003 already included in this release:
  https://github.com/vadz/libtiff/commit/1044b43637fa7f70fb19b93593777b78bd20da86

Patch 0004 already included in this release:
  https://github.com/vadz/libtiff/commit/9a72a69e035ee70ff5c41541c8c61cd97990d018

Patch 0005 already included in this release:
  https://github.com/vadz/libtiff/commit/5c080298d59efa53264d7248bbe3a04660db6ef7

Patch 0006 already included in this release:
  https://github.com/vadz/libtiff/commit/48780b4fcc425cddc4ef8ffdf536f96a0d1b313b

Patch 0007 already included in this release:
  https://github.com/vadz/libtiff/commit/d60332057b9575ada4f264489582b13e30137be1

Patch 0008 already included in this release:
  https://github.com/vadz/libtiff/commit/2ea32f7372b65c24b2816f11c04bf59b5090d05b

Patch 0009 already included in this release:
  https://github.com/vadz/libtiff/commit/8283e4d1b7e53340684d12932880cbcbaf23a8c1

Patch 0010 already included in this release:
  https://github.com/vadz/libtiff/commit/47f2fb61a3a64667bce1a8398a8fcb1b348ff122

Patch 0011 already included in this release:
  https://github.com/vadz/libtiff/commit/3cfd62d77c2a7e147a05bd678524c345fa9c2bb8

Patch 0012 already included in this release:
  https://github.com/vadz/libtiff/commit/0a76a8c765c7b8327c59646284fa78c3c27e5490

Patch 0013 already included in this release:
  https://github.com/vadz/libtiff/commit/66e7bd59520996740e4df5495a830b42fae48bc4

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