Reexamine some dubious-looking code

[tom-seddon]

beeblink/beeb/tube_serial.s65

Line 1447 in 825aa10

lda #get_status_flag_for_dir(\dir)

[tom-seddon]

An extra instruction in the Electron case, I assume dating from when I was first trying to get it even remotely working. Remove, and assess the difference.

(This macro gets used quite a lot, including in some of the unrolled cases, where saving a cycle or two per can add up. The Electron needs all the help it can get!)