soc: riscv: telink_b91: add dfu related configurations for b91 platform

Modify Telink b91 config files and linker script with necessary config
settings required for DFU.

Signed-off-by: Alex Kolosov <rikorsev@gmail.com>

boards/riscv/tlsr9518adk80d/Kconfig.defconfig

@@ -49,4 +49,10 @@ endchoice
 
 endif # BT
 
+# Workaround for not being able to have commas in macro arguments
+DT_CHOSEN_Z_CODE_PARTITION := zephyr,code-partition
+
+config FLASH_LOAD_OFFSET
+	default $(dt_chosen_reg_addr_hex,$(DT_CHOSEN_Z_CODE_PARTITION)) if USE_DT_CODE_PARTITION
+
 endif

soc/riscv/riscv-privilege/telink_b91/Kconfig.defconfig.series

@@ -50,4 +50,7 @@ config TEST_EXTRA_STACK_SIZE
 	int
 	default 1024
 
+config HAS_FLASH_LOAD_OFFSET
+	default y if BOOTLOADER_MCUBOOT
+
 endif # SOC_SERIES_RISCV_TELINK_B91

soc/riscv/riscv-privilege/telink_b91/Kconfig.soc

@@ -36,3 +36,7 @@ config SOC_RISCV_TELINK_B91
 	select INCLUDE_RESET_VECTOR
 
 endchoice
+
+config FLASH_BASE_ADDRESS
+	hex
+	default $(dt_chosen_reg_addr_hex,$(DT_CHOSEN_Z_FLASH))

soc/riscv/riscv-privilege/telink_b91/linker.ld

@@ -21,6 +21,7 @@ SECTIONS
 {
 	SECTION_PROLOGUE(vector,,)
 	{
+		. = CONFIG_ROM_START_OFFSET;
 		. = ALIGN(4);
 		KEEP(*(.init.*))
 	} GROUP_LINK_IN(ROM_INIT)