package/fbtft: add license file

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit 19275a1a56dbd2cebb9ef91430a0364c0d3a1214)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/fbtft/fbtft.hash

@@ -1,2 +1,3 @@
 # locally computed
 sha256  0e81de89fdd7ab810716fc0549e767527f342e829309dee5c2cca1e9d1728770  fbtft-274035404701245e7491c0c6471c5b72ade4d491.tar.gz
+sha256  a9ca80d65a5ef10fe614a6c1e8c8d4d3b96637e8855a96c7cf0fa438526097a7  fbtft-core.c

package/fbtft/fbtft.mk

@@ -7,5 +7,6 @@
 FBTFT_VERSION = 274035404701245e7491c0c6471c5b72ade4d491
 FBTFT_SITE = $(call github,notro,fbtft,$(FBTFT_VERSION))
 FBTFT_LICENSE = GPL-2.0
+FBTFT_LICENSE_FILES = fbtft-core.c
 
 $(eval $(generic-package))