nb/intel/pineview: Move the boilerplate mainboard_romstage_entry

The mainboard_romstage_entry function is mostly boilerplate, so move
it to a common location and provide mainboard specific callbacks.

Change-Id: I33cf1d6a60d272f490f41205ec725dee8b00242b
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/30851
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

src/northbridge/intel/pineview/pineview.h

@@ -235,6 +235,11 @@ u32 decode_igd_memory_size(const u32 gms);
 u32 decode_igd_gtt_size(const u32 gsm);
 u8 decode_pciebar(u32 *const base, u32 *const len);
 
+/* Mainboard romstage callback functions */
+void mb_enable_lpc(void);
+void get_mb_spd_addrmap(u8 *spd_addr_map);
+void mb_pirq_setup(void); /* optional */
+
 struct acpi_rsdp;
 unsigned long northbridge_write_acpi_tables(unsigned long start, struct acpi_rsdp *rsdp);