boot: android: fix booting without a ramdisk

boot: android: fix booting without a ramdisk

android_image_get_ramdisk() will return an error if there is no ramdisk.
Using the android image without a ramdisk worked until commit
1ce8e10f3b4b ("image: Fix up ANDROID_BOOT_IMAGE ramdisk code") because
the return code wasn't checked until then. Return -ENOENT in case
there is no ramdisk and translate that into -ENOPKG in the calling
code, which will then indicate "no ramdisk" to its caller
(boot_get_ramdisk()).

This way, we can get rid of the "*rd_data = *rd_len = 0;" in the error
path, too.

With this, I'm able to boot a linux kernel using fastboot again:

  fastboot --base 0x41000000 --header-version 2 --dtb /path/to/dtb \
  --cmdline "root=/dev/mmcblk0p1 rootwait" boot path/to/Image

Signed-off-by: Michael Walle <mwalle@kernel.org>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Link: https://lore.kernel.org/r/20240729213657.2550935-1-mwalle@kernel.org
Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>