boot/gummiboot: switch to http for git clone

The git:// protocol may not go through conservative corporate firewalls.
Use http, that goes out through about anything.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

boot/gummiboot/gummiboot.mk

@@ -4,7 +4,8 @@
 #
 ################################################################################
 
-GUMMIBOOT_SITE = git://anongit.freedesktop.org/gummiboot
+GUMMIBOOT_SITE = http://cgit.freedesktop.org/gummiboot
+GUMMIBOOT_SITE_METHOD = git
 GUMMIBOOT_VERSION = 43
 GUMMIBOOT_LICENSE = LGPLv2.1+
 GUMMIBOOT_LICENSE_FILES = LICENSE