acpi/acpigen.h: Add more intuitive AML package closing functions

Until now every AML package had to be closed using acpigen_pop_len().
This commit introduces set of package closing functions corresponding
with their opening function names. For example acpigen_write_if()
opens if-statement package, acpigen_write_if_end() closes it.
Now acpigen_write_else() closes previously opened acpigen_write_if(),
so acpigen_pop_len() is not required before it.

Signed-off-by: Jakub Czapiga <jacz@semihalf.com>
Change-Id: Icfdc3804cd93bde049cd11dec98758b3a639eafd
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50910
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Lance Zhao
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/soc/amd/picasso/root_complex.c

@@ -228,8 +228,6 @@ static void acipgen_dptci(void)
 	dptc_call_alib("TABB", (uint8_t *)(void *)&tablet_mode_input,
 			sizeof(tablet_mode_input));
 
-	acpigen_pop_len(); /* If */
-
 	/* Else */
 	acpigen_write_else();