RISC-V: Always generate mapping symbols at the start of the sections.

RISC-V: Always generate mapping symbols at the start of the sections.

Before figuring out the suppress rule of mapping symbol with architecture
(changed back to $x), always generate them at the start of the sections.

gas/
    * config/tc-riscv.c (need_arch_map_symbol): Removed.
    (riscv_mapping_state): Updated.
    (riscv_check_mapping_symbols): Updated.
    * testsuite/gas/riscv/mapping-non-arch.d: Removed.
    * testsuite/gas/riscv/mapping-non-arch.s: Likewise.