package/libgcrypt: fix Thumb mode workaround

Fix the following build failure:

/tmp/ccRqWxnA.s:98: Error: instruction not supported in Thumb16 mode -- `adds ip,fp,r0'

Fixes:
 - http://autobuild.buildroot.org/results/4b96f4e41724e5c9c806a6c7df397a58d1ae1b1e



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>