riscv: module: Fix out-of-bounds relocation access

The current code allows rel[j] to access one element past the end of the
relocation section. Simplify to num_relocations which is equivalent to
the existing size expression.

Fixes: 080c432 ("riscv: optimize ELF relocation function in riscv")
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Reviewed-by: Maxim Kochetkov <fido_max@inbox.ru>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20250409171526.862481-1-samuel.holland@sifive.com
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>

Author: SiFiveHolland

arch/riscv/kernel/module.c

@@ -860,7 +860,7 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
 				}
 
 				j++;
-				if (j > sechdrs[relsec].sh_size / sizeof(*rel))
+				if (j == num_relocations)
 					j = 0;
 
 			} while (j_idx != j);