iwlwifi: pcie: gen2: minor code cleanups in byte table update

One line should be indented less, otherwise it looks like it
belongs into the parentheses, which clearly it doesn't; also
some variables can move into their respective if branches.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20200417131727.a4858aa0441b.I0e70e4a5493fe6b8db6390f9349ff0e7888ab240@changeid