src: Remove unused <cf9_reset.h>

Found using:
diff <(git grep -l '#include <cf9_reset.h>' -- src/) <(git grep -l 'RST_CNT\|FULL_RST\|RST_CPU\|SYS_RST\|do_system_reset\|do_full_reset\|cf9_reset_prepare\|system_reset\|full_reset' -- src/) |grep "<"

Change-Id: I093d8412e14ce81b462fb9a7ccb3a2a93ae760a6
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60803
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin L Roth <gaumless@tutanota.com>

src/security/intel/txt/romstage.c

@@ -2,7 +2,6 @@
 
 #include <arch/cpu.h>
 #include <arch/mmio.h>
-#include <cf9_reset.h>
 #include <console/console.h>
 #include <cpu/intel/common/common.h>
 #include <cpu/x86/cr.h>