package/intel-gmmlib: fix license file and add hash

The license file is not named COPYING, but LICENSE.md. While we're at
it, we add the hash of the license file.

Fixes:

  http://autobuild.buildroot.net/results/09e4c14effe58ec2bc6f3deede7cc17ae6590767/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/intel-gmmlib/intel-gmmlib.hash

@@ -1,2 +1,3 @@
 # Locally computed
 sha256 7970a8ae4e16efb98f38fbbc0346eea03227fc4462a9bd8e8077277cc3430a84  intel-gmmlib-18.4.1.tar.gz
+sha256 b61d639c5d84ec710ffcf5600ac92f8a4ace66670c1f9bd921f3bde671d36033  LICENSE.md

package/intel-gmmlib/intel-gmmlib.mk

@@ -7,7 +7,7 @@
 INTEL_GMMLIB_VERSION = 18.4.1
 INTEL_GMMLIB_SITE = https://github.com/intel/gmmlib/archive
 INTEL_GMMLIB_LICENSE = MIT
-INTEL_GMMLIB_LICENSE_FILES = COPYING
+INTEL_GMMLIB_LICENSE_FILES = LICENSE.md
 
 INTEL_GMMLIB_INSTALL_STAGING = YES
 INTEL_GMMLIB_SUPPORTS_IN_SOURCE_BUILD = NO