staging: ks7010: move skb null check near allocation

Currently, after allocating an sk_buff, driver fills the sk_buff
within code block guarded by a NULL check on the sk_buff. If a NULL
check is done immediately after the allocation, and code returns on
error, then the subsequent code need not be guarded and the level of
indentation may be reduced. This aids the readability of the code and
makes explicit the error path.

Check for NULL directly after allocating the sk_buff, return if
allocation fails. Reduce indentation of subsequent code. Do not change
the program logic.

Signed-off-by: Tobin C. Harding <me@tobin.cc>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>