soc/mediatek: Move emi.c to common folder

The emi.c is the same for MT8186 and MT8188, so we could move it to
the common folder and reuse it.

TEST=build pass
BUG=b:236331724

Signed-off-by: Bo-Chen Chen <rex-bc.chen@mediatek.com>
Change-Id: I225f1d07c973129172f01bf7f4d7f5d5abe7c02b
Reviewed-on: https://review.coreboot.org/c/coreboot/+/66328
Reviewed-by: Yidi Lin <yidilin@chromium.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/mediatek/common/emi.c

@@ -1,10 +1,5 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
-/*
- * This file is created based on MT8186 Functional Specification
- * Chapter number: 4.8
- */
-
 #include <assert.h>
 #include <cbmem.h>
 #include <commonlib/bsd/mem_chip_info.h>

src/soc/mediatek/mt8186/Makefile.inc

@@ -19,7 +19,7 @@ bootblock-y += ../common/wdt.c ../common/wdt_req.c wdt.c
 romstage-y += ../common/cbmem.c
 romstage-y += ../common/dram_init.c
 romstage-y += ../common/dramc_param.c
-romstage-y += emi.c
+romstage-y += ../common/emi.c
 romstage-y += ../common/memory.c
 romstage-y += ../common/memory_test.c
 romstage-y += ../common/mmu_operations.c ../common/mmu_cmops.c
@@ -31,7 +31,7 @@ ramstage-y += ../common/ddp.c ddp.c
 ramstage-y += devapc.c
 ramstage-y += ../common/dfd.c
 ramstage-y += ../common/dsi.c ../common/mtk_mipi_dphy.c
-ramstage-y += emi.c
+ramstage-y += ../common/emi.c
 ramstage-y += ../common/mcu.c
 ramstage-y += ../common/mmu_operations.c ../common/mmu_cmops.c
 ramstage-$(CONFIG_COMMONLIB_STORAGE_MMC) += ../common/msdc.c msdc.c