KVM: selftests: kvm_vm_elf_load() and elfhdr_get() should close fd

kvm_vm_elf_load() and elfhdr_get() open one file each, but they
never close the opened file descriptor.  If a test repeatedly
creates and destroys a VM with __vm_create(), which
(directly or indirectly) calls those two functions, the test
might end up getting a open failure with EMFILE.
Fix those two functions to close the file descriptor.
Signed-off-by: Reiji Watanabe <reijiw@google.com>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Reviewed-by: Andrew Jones <andrew.jones@linux.dev>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20221220170921.2499209-2-reijiw@google.comSigned-off-by: Sean Christopherson <seanjc@google.com>

tools/testing/selftests/kvm/lib/elf.c

@@ -90,6 +90,7 @@ static void elfhdr_get(const char *filename, Elf64_Ehdr *hdrp)
 		"  hdrp->e_shentsize: %x\n"
 		"  expected: %zx",
 		hdrp->e_shentsize, sizeof(Elf64_Shdr));
+	close(fd);
 }
 
 /* VM ELF Load
@@ -190,4 +191,5 @@ void kvm_vm_elf_load(struct kvm_vm *vm, const char *filename)
 				phdr.p_filesz);
 		}
 	}
+	close(fd);
 }