[ELF][test] Update znotext-plt-relocations.s to emit R_X86_64_PC32

This is a leftover from r325379.

The intention of this test was to check in a non-pic link, R_X86_64_PC32
to a STT_FUNC created a PLT. However, after the llvm-mc change in
r325569, this code path is no longer exercised. Use the r325379 trick to
keep testing R_X86_64_PC32.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@362095 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/ELF/znotext-plt-relocations.s b/test/ELF/znotext-plt-relocations.s
index ad305b0..3bc1f41 100644
--- a/test/ELF/znotext-plt-relocations.s
+++ b/test/ELF/znotext-plt-relocations.s
@@ -16,5 +16,6 @@
 
 .text
 _start:
-callq atexit
+.byte 0xe8
+.long atexit - . - 4
 .quad foo