README: Update instructions for building a flashable image

Signed-off-by: Nhi Pham <npham@amperecomputing.com>

Makefile

@@ -284,6 +284,8 @@ tianocore_img: _check_atf_slim _check_board_setting tianocore_fd
 		dd bs=1024 seek=2048 if=$(OUTPUT_FD_IMAGE) of=$(OUTPUT_RAW_IMAGE); \
 	fi
 
+# For Ampere ATF version 1.03 and 2.01, the following supports adding 4MB padding to the final image for
+# compatibility with the support of firmware update utility.
 	@if [ $(ATF_MAJOR)$(ATF_MINOR) -eq 103 ] || [ $(ATF_MAJOR)$(ATF_MINOR) -eq 201 ]; then \
 		dd if=/dev/zero bs=1024 count=4096 | tr "\000" "\377" > $(OUTPUT_IMAGE); \
 		dd bs=1 seek=4194304 conv=notrunc if=$(OUTPUT_RAW_IMAGE) of=$(OUTPUT_IMAGE); \

README.md

@@ -87,17 +87,8 @@ $ python nvparam.py -f Platform/Ampere/JadePkg/jade_board_setting.txt -o BUILDS/
 
 ### Build integrated UEFI + Board Setting + ATF image
 
-For Ampere ATF 1.03 and later version
-```
-$ dd bs=1024 count=6144 if=/dev/zero | tr "\000" "\377" > BUILDS/jade_tianocore_atf/jade_tianocore_atf.img
-$ dd bs=1 seek=4194304 conv=notrunc if=<ampere_atf_image_filepath> of=BUILDS/jade_tianocore_atf/jade_tianocore_atf.img
-$ dd bs=1 seek=6225920 conv=notrunc if=BUILDS/jade_tianocore_atf/jade_board_setting.bin of=BUILDS/jade_tianocore_atf/jade_tianocore_atf.img
-$ dd bs=1024 seek=6144 if=BUILDS/jade_tianocore_atf/jade_tianocore.fip.signed of=BUILDS/jade_tianocore_atf/jade_tianocore_atf.img
+Generating the final image with the following commands:
 
-Result: BUILDS/jade_tianocore_atf/jade_tianocore_atf.img
-```
-
-For Ampere ATF 1.02 version
 ```
 $ dd bs=1024 count=2048 if=/dev/zero | tr "\000" "\377" > BUILDS/jade_tianocore_atf/jade_tianocore_atf.img
 $ dd bs=1 conv=notrunc if=<ampere_atf_image_filepath> of=BUILDS/jade_tianocore_atf/jade_tianocore_atf.img
@@ -107,6 +98,8 @@ $ dd bs=1024 seek=2048 if=BUILDS/jade_tianocore_atf/jade_tianocore.fip.signed of
 Result: BUILDS/jade_tianocore_atf/jade_tianocore_atf.img
 ```
 
+Note that the `jade_tianocore_atf.img` image is flashed at the beginning of the ATF SLIM region according to the SPI-NOR Flash Layout.
+
 ### Build Tianocore Capsule
 
 For current Ampere ATF