ethernet: 3c509: Fix most coding style issues

ethernet: 3c509: Fix most coding style issues

Update the driver for our current coding style according to output from
`checkpatch.pl' and manual code review, where no change to binary code
results, as indicated by `objdump -dr'.  Exceptions are as follows:

- incomplete reverse xmas tree in set_multicast_list(), as that would
  change binary output,

- referring el3_start_xmit() verbatim rather than via `__func__' with
  pr_debug(), likewise,

- a bunch of pr_cont() calls, likewise,

- a long udelay() call in el3_netdev_set_ecmd() made under a spinlock,
  likewise plus it's not eligible for conversion to a sleep in the first
  place,

- a blank line at the start of a block in el3_interrupt(), to improve
  readability where the first statement would otherwise visually merge
  with the controlling expression of the enclosing `while' statement.

These issues are benign and depending on circumstances may be adressed
with suitable code refactoring later on.

Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
Link: https://patch.msgid.link/alpine.DEB.2.21.2605201208280.1450@angie.orcam.me.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>