term/serial: Avoid double lookup of serial ports

The various functions to add a port used to return port->name, and
the callers would immediately iterate all registered ports to "find"
the one just created by comparing that return value with ... port->name.

This is a waste of cycles and code. Instead, have those functions
return "port" directly.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/term/ns8250-spcr.c

@@ -24,7 +24,7 @@
 #include <grub/dl.h>
 #include <grub/acpi.h>
 
-char *
+struct grub_serial_port *
 grub_ns8250_spcr_init (void)
 {
   struct grub_acpi_spcr *spcr;