package/fluidsynth: bump to version 2.1.1

- This will fix a static build failure with readline thanks to
  https://github.com/FluidSynth/fluidsynth/commit/c538c9fa7e392ce16c3354696e7dc7781a78a300
- Update indentation of hash file (two spaces)

Fixes:
 - http://autobuild.buildroot.org/results/88609eefe55af2ca50d43e17d3424b923528b07a



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>