native: renamed "full" variant to "picotool"

It looks like then uploading to combined image using the BOOT button and
file copy, it'll only upload the ELF part. Only picotool transfers the
full file. So the image has been renamed to "picotool" to make this as
obvious as possible. Documentation also update to make this clear.

Signed-off-by: Sven Oliver Moll <svolli@svolli.de>

doc/README_release.txt

@@ -32,6 +32,13 @@ sorbus-computer-native_cpmfs.uf2:
 The filesystem image containing a CP/M-65 installation for the Native
 system.
 
-sorbus-computer-native_alpha_full.uf2:
+sorbus-computer-native_alpha_picotoool.uf2:
 This image contains all data for the Native system in one file: firmware,
-kernel and filesystem image.
+kernel and filesystem image. Only works when using picotool for loading.
+
+For uploading the native firmware on the Sorbus the following order is
+suggested:
+- sorbus-computer-native_cpmfs.uf2
+- sorbus-computer-native_kernel.uf2
+- sorbus-computer-native_alpha.uf2
+

src/rp2040/CMakeLists.txt

@@ -149,14 +149,14 @@ target_link_libraries(native_alpha
 setup_target(native_alpha)
 # firmware for Native core
 add_custom_target(native_firmware ALL
-   DEPENDS native_alpha_full native_rom
+   DEPENDS native_alpha_picotool native_rom
 )
 bbin2uf2(native_rom 0x103FE000 native_kernel)
 bin2uf2(native_cpmfs 0x10400000 native_cpmfs.dhara)
-uf2join(native_alpha_full
-   native_alpha
+uf2join(native_alpha_picotool
    native_rom
    native_cpmfs
+   native_alpha
 )
 gencpmfs(native_cpmfs.img)
 dharawrite(native_cpmfs.dhara native_cpmfs.img)