amdfwtool: Move some funtions to other categorized source files

To reduce the size of amdfwtool.c which is already too big.

Change-Id: Ib80eeb42f59a3dda04402b2feaadc1d178ed989e
Signed-off-by: Zheng Bao <fishbaozi@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/73910
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Fred Reitberger <reitbergerfred@gmail.com>

util/amdfwtool/Makefile.inc

@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: BSD-3-Clause
 
-amdfwtoolobj = amdfwtool.o data_parse.o
+amdfwtoolobj = amdfwtool.o data_parse.o signed_psp.o handle_file.o
 amdfwreadobj = amdfwread.o
 
 AMDFWTOOLCFLAGS=-O2 -Wall -Wextra -Wshadow -Werror