Handle the PLT32 reloacation errors for kernels binaries built with binutils
newer then 2.31, similar to:
[    5.742485] module: autofs4: Unknown rela relocation: 4
[    5.742536] systemd[1]: Failed to insert module 'autofs4': Exec format error

This patch is based on a mainline kernel patch b21ebf2fb4cde1618915a97cc773e287ff49173e
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Wed, 7 Feb 2018 14:20:09 -0800
Subject: x86: Treat R_X86_64_PLT32 as R_X86_64_PC32

Signed-off-by: Woody Suwalski <terraluna977@gmail.com>

--- a/arch/x86/tools/relocs.c	2020-01-24 18:48:09.477919152 -0500
+++ b/arch/x86/tools/relocs.c	2020-01-24 18:48:53.645612045 -0500
@@ -763,6 +763,7 @@ static int do_reloc64(struct section *se
 	switch (r_type) {
 	case R_X86_64_NONE:
 	case R_X86_64_PC32:
+	case R_X86_64_PLT32:
 		/*
 		 * NONE can be ignored and PC relative relocations don't
 		 * need to be adjusted.
--- a/arch/x86/kernel/module.c	2020-01-24 18:46:54.922670590 -0500
+++ b/arch/x86/kernel/module.c	2020-01-24 18:47:46.714112016 -0500
@@ -180,6 +180,7 @@ int apply_relocate_add(Elf64_Shdr *sechd
 				goto overflow;
 			break;
 		case R_X86_64_PC32:
+		case R_X86_64_PLT32:
 			val -= (u64)loc;
 			*(u32 *)loc = val;
 #if 0