Revert "[compiler-rt][RISCV] Implement __init_riscv_feature_bits (llvm#85790)"

This reverts commit a41a4ac.

Author: BeMg

compiler-rt/lib/builtins/CMakeLists.txt

@@ -739,7 +739,6 @@ endif()
 set(powerpc64le_SOURCES ${powerpc64_SOURCES})
 
 set(riscv_SOURCES
-  riscv/feature_bits.c
   riscv/fp_mode.c
   riscv/save.S
   riscv/restore.S