libimobiledevice: fix dependency on libtatsu

libimobiledevice: fix dependency on libtatsu

libtatsu is a dependency only for libimobiledevice-utils
the library itself does not use it during build, and is a
core component for iPhone tethering, while the utils are optional

move the dependency to the utils, to reduce the build size:
libtatsu depends on libcurl, which is compiled with a TLS library,
so users of prebuilt packages are forced to install both
OpenSSL and mbed TLS. This patch removes the unnecessary dependency.

Fixes: https://github.com/openwrt/packages/issues/28427
Signed-off-by: Georgi Valkov <gvalkov@gmail.com>