boot/espressif: Add CMakeLists.txt and mcuboot_config.h

Add sources and headers required for build

Signed-off-by: Shubham Kulkarni <shubham.kulkarni@espressif.com>
diff --git a/boot/espressif/include/sysflash/sysflash.h b/boot/espressif/include/sysflash/sysflash.h
new file mode 100644
index 0000000..7f0fb28
--- /dev/null
+++ b/boot/espressif/include/sysflash/sysflash.h
@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2021 Espressif Systems (Shanghai) Co., Ltd.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+//! A user-defined identifier for different storage mediums
+//! (i.e internal flash, external NOR flash, eMMC, etc)
+#define FLASH_DEVICE_INTERNAL_FLASH 0
+
+//! An arbitrarily high slot ID we will use to indicate that
+//! there is not slot
+#define FLASH_SLOT_DOES_NOT_EXIST 255
+
+//! NB: MCUboot expects this define to exist but it's only used
+//! if MCUBOOT_SWAP_USING_SCRATCH=1 is set
+#define FLASH_AREA_IMAGE_SCRATCH FLASH_SLOT_DOES_NOT_EXIST
+
+//! The slot we will use to track the bootloader allocation
+#define FLASH_AREA_BOOTLOADER 0
+
+//! A mapping to primary and secondary/upgrade slot
+//! given an image_index. We'll plan to use
+#define FLASH_AREA_IMAGE_PRIMARY(i) ((i == 0) ? 1 : 255)
+#define FLASH_AREA_IMAGE_SECONDARY(i) ((i == 0) ? 2 : 255)