Fix support for RAM-less multi-processor init

Fix regression after commit:
  7dfe32c540

Only align 16-bit entry on platforms that really require it,
indicated by selecting SIPI_VECTOR_IN_ROM in CPU Kconfig.
Disable assertion test of AP_SIPI_VECTOR for platforms not
depending on this feature.

Build of romstage should be fixed to get the vector address from
bootblock build automatically.

Change-Id: Ide470833c0254df1a9ff708369ab1c095ccfb98d
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/875
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/cpu/intel/socket_mPGA604/Kconfig

@@ -11,6 +11,7 @@ config SOCKET_SPECIFIC_OPTIONS # dummy
 	select MMX
 	select SSE
 	select UDELAY_TSC
+	select SIPI_VECTOR_IN_ROM
 
 # mPGA604 are usually Intel Netburst CPUs which should have SSE2
 # but the ramtest.c code on the Dell S1850 seems to choke on