cpu/x86/smm: Fix size_t type mismatch in print statement

The 64-bit compiler x86_64-linux-gnu-gcc-10 aborts the build with the
format warning below:

        CC         ramstage/cpu/x86/smm/smm_module_loader.o
    src/cpu/x86/smm/smm_module_loader.c: In function 'smm_module_setup_stub':
    src/cpu/x86/smm/smm_module_loader.c:360:70: error: format '%lx' expects argument of type 'long unsigned int', but argument 5 has type 'unsigned int' [-Werror=format=]
      360 |   printk(BIOS_ERR, "%s: state save size: %zx : smm_entry_offset -> %lx\n",
          |                                                                    ~~^
          |                                                                      |
          |                                                                      long unsigned int
          |                                                                    %x

As `size_t` is defined as `long unsigned int` in i386-elf (32-bit), the
length modifier `l` matches there. With x86_64-elf/x86_64-linux-gnu
(64-bit) and `-m32` `size_t` is defined as `unsigned int` resulting in a
type mismatch. So, use the correct length modifier `z` for the type
`size_t`.

Found-by: x86_64-linux-gnu-gcc-10 (Debian 10.2.1-6) 10.2.1 20210110
Fixes: afb7a814 ("cpu/x86/smm: Introduce SMM module loader version 2")
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Change-Id: I4172e0f4dc40437250da89b7720a5c1e5fbab709
Reviewed-on: https://review.coreboot.org/c/coreboot/+/54342
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>
diff --git a/src/cpu/x86/smm/smm_module_loader.c b/src/cpu/x86/smm/smm_module_loader.c
index 6d999a7..9f0ae92 100644
--- a/src/cpu/x86/smm/smm_module_loader.c
+++ b/src/cpu/x86/smm/smm_module_loader.c
@@ -356,7 +356,7 @@
 	/* The save state size encroached over the first SMM entry point. */
 	if (size <= SMM_ENTRY_OFFSET) {
 		printk(BIOS_ERR, "%s: encroachment over SMM entry point\n", __func__);
-		printk(BIOS_ERR, "%s: state save size: %zx : smm_entry_offset -> %lx\n",
+		printk(BIOS_ERR, "%s: state save size: %zx : smm_entry_offset -> %zx\n",
 		       __func__, size, (size_t)SMM_ENTRY_OFFSET);
 		return -1;
 	}