lib/oe/patch: handle non-UTF8 encoding when reading patches

lib/oe/patch: handle non-UTF8 encoding when reading patches

When extracting patches from a git repository with PATCHTOOL = "git" we
cannot assume that all patches will be UTF-8 formatted, so as with other
places in this module, try latin-1 if utf-8 fails.

This fixes UnicodeDecodeError running devtool update-recipe or devtool
finish on the openssl recipe.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>