lib/prog_loaders: Add payload_preload

This method will allow the SoC code to start loading the payload before
it is required.

BUG=b:177909625
TEST=Boot guybrush and see read/decompress drop by 23 ms.

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: Ifa8f30a0f4f931ece803c2e8e022e4d33d3fe581
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56051
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>

src/lib/Kconfig

@@ -98,3 +98,14 @@ config NO_CBFS_MCACHE
 	  the associated CAR/SRAM size. In that case every single CBFS file
 	  lookup must re-read the same CBFS directory entries from flash to find
 	  the respective file.
+
+config PAYLOAD_PRELOAD
+	bool
+	depends on COOP_MULTITASKING
+	help
+	  On some systems with SPI DMA controllers, it is possible to preload
+	  the payload while ramstage is executing. This can be selected by the
+	  SoC to enable payload preloading.
+
+	  The SoC needs to define a payload_preload_cache region where the
+	  raw payload can be placed.