Leave OER support in asn1c enabled

OER can be disable with the switch -DASN_DISABLE_OER_SUPPORT. In F1AP,
disabling OER leads to a typedef void a_type; leading to lots of compilation
errors because of illegal void variable declarations. This commit leaves OER
support enabled, avoiding this error.

cmake_targets/CMakeLists.txt

@@ -175,7 +175,6 @@ set(CMAKE_C_FLAGS
 set(CMAKE_CXX_FLAGS
   "${CMAKE_CXX_FLAGS} ${C_FLAGS_PROCESSOR} -std=c++11 -D'MAKE_VERSION(a,b,c)=((a)*256+(b)*16+c)'"
 )
-add_definitions("-DASN_DISABLE_OER_SUPPORT")
 
 
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