Other libraries already use ASN1C_PREFIX except the HNBAP one. Let's use
it here to avoid collisions.
All new include/osmocom/hnbap/HNBAP_*.h and src/hnbap/HNBAP_*.c are
generated using the updated src/hnbap/Makefile.am.
Files such as src/*.c, test/* and include/osmocom/hnbap/hnbap_common.h
are modified manually to update structs/enums to new prefix.
Related: SYS#5516
Change-Id: I6c062f631527ae42811bfec134933671c05ecba6