Fix feeless_if in pallet section

[eagr]

fixes #5981

Could confirm the issue with the added tests:

test tests/split_ui/pass/split_call.rs [should pass] ... error
┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈
error[E0423]: expected value, found attribute macro `origin`
  --> tests/split_ui/pass/split_call.rs:23:1
   |
23 | #[frame_support::pallet(dev_mode)]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not a value
   |
   = note: this error originates in the attribute macro `frame_support::pallet` (in Nightly builds, run with -Z macro-backtrace for more info)

Description

origin unexpectedly resolved to a macro, which is available at the span of invocation. The solution here is to use the expansion as a function instead of a call and pass in the desired values to avoid ambiguities.

[gui1117]

Looks good to me, but needs to fix clippy warning (so user using clippy are not bothered).