tslib: use upstream .tar.xz archive

Save some network bandwidth.

[Peter: use TSLIB_VERSION instead of hardcoding 1.3]
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Tested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/tslib/tslib.hash

@@ -1,2 +1,2 @@
 # Locally generated
-sha256  599f51c265158e7801b166e879e19759e8d3e5fdf2fa99c630698fe162a41d56  tslib-1.3.tar.gz
+sha256  e935101adca980a14d1a13362796222575f99e6a41db585e8358fffddb98d92c  tslib-1.3.tar.xz

package/tslib/tslib.mk

@@ -6,6 +6,7 @@
 
 TSLIB_VERSION = 1.3
 TSLIB_SITE = https://github.com/kergoth/tslib/releases/download/$(TSLIB_VERSION)
+TSLIB_SOURCE = tslib-$(TSLIB_VERSION).tar.xz
 TSLIB_LICENSE = GPL, LGPL
 TSLIB_LICENSE_FILES = COPYING