disas/libvixl: Fix wrong format strings

When the compiler is told to check the arguments of AppendToOutput,
it reports several errors of this kind:

error: format ‘%d’ expects argument of type ‘int’,
 but argument 3 has type ‘int64_t {aka long int}’ [-Werror=format]

Fix those bugs by using the correct format strings with PRId64, PRIx64.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Message-id: 1403113751-19799-1-git-send-email-sw@weilnetz.de
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
