serial: 8250: Fix 8250_rsa symbol loop

serial: 8250: Fix 8250_rsa symbol loop

Depmod fails for a kernel made with:
  make allnoconfig
  echo -e "CONFIG_MODULES=y\nCONFIG_SERIAL_8250=m\nCONFIG_SERIAL_8250_EXTENDED=y\nCONFIG_SERIAL_8250_RSA=y" >> .config
  make olddefconfig

...due to a dependency loop:

  depmod: ERROR: Cycle detected: 8250 -> 8250_base -> 8250
  depmod: ERROR: Found 2 modules in dependency cycles!

This is caused by the move of 8250 RSA code from 8250_port.c (in
8250_base.ko) into 8250_rsa.c (in 8250.ko) by the commit 5a128fb475fb
("serial: 8250: move RSA functions to 8250_rsa.c"). The commit
b20d6576cdb3 ("serial: 8250: export RSA functions") tried to fix a
missing symbol issue with EXPORTs but those then cause this dependency
cycle.

Break dependency loop by moving 8250_rsa.o from 8250.ko to 8250_base.ko
and by passing univ8250_port_base_ops to univ8250_rsa_support() that
can make a local copy of it.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: Alex Davis <alex47794@gmail.com>
Fixes: 5a128fb475fb ("serial: 8250: move RSA functions to 8250_rsa.c")
Fixes: b20d6576cdb3 ("serial: 8250: export RSA functions")
Cc: stable <stable@kernel.org>
Link: https://lore.kernel.org/all/87frc3sd8d.fsf@posteo.net/
Link: https://lore.kernel.org/all/CADiockCvM6v+d+UoFZpJSMoLAdpy99_h-hJdzUsdfaWGn3W7-g@mail.gmail.com/
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://patch.msgid.link/20251110105043.4062-1-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>