fdt: boot_get_fdt: remove redundant zeroing out

fdt: boot_get_fdt: remove redundant zeroing out

Paranoid programming [1] lies at the foundation of proper software
development, but the repetitive zeroing-out of output arguments in the
context of the same function rather clutters the code and inhibits
further refactoring/optimization than is doing any good.

In boot_get_fdt(), we already perform zero/NULL-initialization of
*of_flat_tree and *of_size at the beginning of the function, so doing
the same at function error-out is redundant/superfluous.

Moreover, keeping the code unchanged might encourage the developers to
update *of_flat_tree and *of_size during some interim computations,
which is against the current design of boot_get_fdt(). Currently,
writing useful data into these arguments happens just before
successfully returning from boot_get_fdt() and it should better stay so.

[1] https://blog.regehr.org/archives/1106

Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Reviewed-by: Simon Glass <sjg@chromium.org>