board: dragonboard410c: Drop custom reduced malloc size

board: dragonboard410c: Drop custom reduced malloc size

At the moment, the dragonboard410c_defconfig specifies a custom
SYS_MALLOC_LEN, lower than the default for Qualcomm boards defined in
arch/arm/mach-snapdragon/Kconfig. It looks like it's too low, since
flashing larger sparse partition images using Fastboot fails with:

  FAILED (remote: 'Malloc failed for: CHUNK_TYPE_RAW')

We are not really that memory-constrained for U-Boot on DB410c, so fix
this by just dropping the custom malloc size and using the default.

Signed-off-by: Stephan Gerhold <stephan.gerhold@linaro.org>
Reviewed-by:
Reviewed-by: Sumit Garg <sumit.garg@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250417-db410c-fixes2-v1-2-76ad994da152@linaro.org
Signed-off-by: Casey Connolly <casey.connolly@linaro.org>