riscv/kexec: handle R_RISCV_CALL_PLT relocation type

R_RISCV_CALL has been deprecated and replaced by R_RISCV_CALL_PLT. See Enum
18-19 in Table 3. Relocation types here:

https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/master/riscv-elf.adoc

It was deprecated in ("Deprecated R_RISCV_CALL, prefer R_RISCV_CALL_PLT"):

riscv-non-isa/riscv-elf-psabi-doc@a0dced8

Recent tools (at least GNU binutils-2.40) already use R_RISCV_CALL_PLT.
Kernels built with such binutils fail kexec_load_file(2) with:

 kexec_image: Unknown rela relocation: 19
 kexec_image: Error loading purgatory ret=-8

The binary code at the call site remains the same, so tell
arch_kexec_apply_relocations_add() to handle _PLT alike.

Fixes: 838b3e2 ("RISC-V: Load purgatory in kexec_file")
Signed-off-by: Torsten Duwe <duwe@suse.de>
Signed-off-by: Petr Tesarik <petr.tesarik.ext@huawei.com>
Cc: Li Zhengyu <lizhengyu3@huawei.com>
Cc: stable@vger.kernel.org
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/all/b046b164af8efd33bbdb7d4003273bdf9196a5b0.1690365011.git.petr.tesarik.ext@huawei.com/
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: Torsten Duwe

arch/riscv/kernel/elf_kexec.c

@@ -425,6 +425,7 @@ int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
 		 * sym, instead of searching the whole relsec.
 		 */
 		case R_RISCV_PCREL_HI20:
+		case R_RISCV_CALL_PLT:
 		case R_RISCV_CALL:
 			*(u64 *)loc = CLEAN_IMM(UITYPE, *(u64 *)loc) |
 				 ENCODE_UJTYPE_IMM(val - addr);