soc/intel: common,apl,skl: remove orphaned memory locking API

Remove the now orphaned memory locking API that was replaced by a
Kconfig-based approach.

Change-Id: Iebc45f514c576d77f90f558151d25c21f0554779
Signed-off-by: Michael Niewöhner <foss@mniewoehner.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36515
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/soc/intel/apollolake/cpu.c

@@ -291,9 +291,3 @@ void apollolake_init_cpus(struct device *dev)
 		CONFIG(BOOT_DEVICE_SPI_FLASH))
 		fast_spi_cache_bios_region();
 }
-
-void cpu_lock_sgx_memory(void)
-{
-	/* Do nothing because MCHECK while loading microcode and enabling
-	 * IA untrusted mode takes care of necessary locking */
-}