soc/amd/common/fsp/fsp-acpi: rework HOB pointer validity check

Checking if the return value of the fsp_find_extension_hob_by_guid call
is NULL should make the code a bit easier to read.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: I6bdb07eab6da80f46c57f5d7b3c894b41ac23b8a
Reviewed-on: https://review.coreboot.org/c/coreboot/+/66699
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>

src/soc/amd/common/fsp/fsp-acpi.c

@@ -23,7 +23,7 @@ uintptr_t add_agesa_fsp_acpi_table(guid_t guid, const char *name, acpi_rsdp_t *r
 	size_t hob_size;
 
 	data = fsp_find_extension_hob_by_guid(guid.b, &hob_size);
-	if (!data) {
+	if (data == NULL) {
 		printk(BIOS_ERR, "AGESA %s ACPI table was not found.\n", name);
 		return current;
 	}