package/openal: bump to version 1.20.1

package/openal: bump to version 1.20.1

This will fix the build with gcc 10 due to the library codebase being
switched to C++11.

It should be noted that bumping the C++ requirement from C++11 to C++14
is not needed for this bump as this change is not yet in this version:
https://github.com/kcat/openal-soft/commit/f6a0b004e0424e1f12a226b3b3c7193063eb02e3

Also update indentation in hash file (two spaces)

Fixes:
 - http://autobuild.buildroot.org/results/4546ce4f176164462b0e73c387bc45c9771f98f7

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