drivers/amd/agesa: Use prepare_and_run_postcar

This removes some of the postcar setup boilerplate.

Change-Id: I4f8f92b88ac16dd70ff4878dfc14e676386d4703
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/61962
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Michał Żygowski <michal.zygowski@3mdeb.com>

src/northbridge/amd/agesa/agesa_helper.h

@@ -36,7 +36,6 @@ void EmptyHeap(void);
 #define HIGH_MEMORY_SCRATCH		0x30000
 
 void fixup_cbmem_to_UC(int s3resume);
-void recover_postcar_frame(struct postcar_frame *pcf, int s3resume);
 
 void restore_mtrr(void);
 void backup_mtrr(void *mtrr_store, u32 *mtrr_store_size);