Merge common EC directories

Split the EC define into base and variant. Merge the 3 ATmega chips as
atmega, and the 2 ITE chips as ite.

Tested that the generated files are identical.

Signed-off-by: Tim Crawford <tcrawford@system76.com>

src/ec/ite/ec.mk

@@ -1,12 +1,18 @@
 # SPDX-License-Identifier: GPL-3.0-only
 
+ifeq ($(EC_VARIANT), it8587e)
+# SRAM is 4096 bytes, but SRAM at address 2048 is used for scratch ROM
+SRAM_SIZE=2048
+else ifeq ($(EC_VARIANT), it5570e)
+# SRAM is 6144 bytes, only 4096 bytes are mapped at address 0. Region at
+# 0x0E00-0x1000 is used for AP communication. So this is brought down to 2048,
+# which matches it8587e limits
+SRAM_SIZE=2048
+else
+$(error Unsupported EC: $(EC_VARIANT))
+endif
+
 ARCH=8051
 
 # 64 KB is the max without banking
 CODE_SIZE=65536
-
-# Include ITE common source
-EC_ITE_COMMON_DIR=src/ec/ite
-SRC+=$(wildcard $(EC_ITE_COMMON_DIR)/*.c)
-INCLUDE+=$(wildcard $(EC_ITE_COMMON_DIR)/include/ec/*.h) $(EC_ITE_COMMON_DIR)/ec.mk
-CFLAGS+=-I$(EC_ITE_COMMON_DIR)/include