serial: 8250: remove CONFIG_SERIAL_8250_RSA inline macros from code

serial: 8250: remove CONFIG_SERIAL_8250_RSA inline macros from code

All these:
  #ifdef CONFIG_SERIAL_8250_RSA
  ...
  #endif

in the 8250 generic code distract the reader. Introduce empty inlines to
handle the !CONFIG_SERIAL_8250_RSA case and handle the '#if's around the
RSA functions definitions.

This means rsa_autoconfig() and rsa_reset() functions were introduced to
contain the particular code.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20250611100319.186924-10-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>