Define GOT-Relative data relocation

This introduces a new relocation `R_RISCV_GOT32_PCREL` follows the existing
wording to “R_RISCV_32_PCREL”, but instead evaluates to the 32-bit offset
between a GOT entry for a given symbol and the current location where the
relocation is applied, so its equation would be “G + GOT - P + A”.

Author: PiJoules

riscv-elf.adoc

@@ -467,8 +467,10 @@ Description:: Additional information about the relocation
 .2+| 64      .2+| TLSDESC_ADD_LO12  .2+| Static  | _I-Type_          .2+| Low 12 bits of a 32-bit PC-relative offset into a TLS descriptor entry, `%tlsdesc_add_lo(address of %tlsdesc_hi)`, the addend must be 0
                                             <| S - P
 .2+| 65      .2+| TLSDESC_CALL      .2+| Static  |                   .2+| Annotate call to TLS descriptor resolver function, `%tlsdesc_call(address of %tlsdesc_hi)`, for relaxation purposes only
+.2+| 66      .2+| 32_PCREL      .2+| Static  | _word32_          .2+| 32-bit PC relative offset to the GOT entry for a symbol
+                                            <| G + GOT - P + A
                                             <|
-.2+| 66-191  .2+| *Reserved*                          .2+| -       |                   .2+| Reserved for future standard use
+.2+| 67-191  .2+| *Reserved*                          .2+| -       |                   .2+| Reserved for future standard use
                                             <|
 .2+| 192-255 .2+| *Reserved*                          .2+| -       |                   .2+| Reserved for nonstandard ABI extensions
                                             <|