arch/x86/acpigen: refactor calls to acpigen_write_register

All of the callers to acpigen_write_register() also make calls to
acpigen_write_resourcetemplate_[header|footer](). This change introduces
acpigen_write_register_resource() to unify all of those trio of calls
into one.  I also made the input parameter const.

Change-Id: I10b336acf9f03c423bee9dc38955b1617e11c025
Signed-off-by: Matt Delco <delco@chromium.org>
Reviewed-on: https://review.coreboot.org/27672
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/arch/x86/acpigen.c b/src/arch/x86/acpigen.c
index 732f749..a614efb 100644
--- a/src/arch/x86/acpigen.c
+++ b/src/arch/x86/acpigen.c
@@ -578,14 +578,10 @@
 	acpigen_write_package(2);
 
 	/* ControlRegister */
-	acpigen_write_resourcetemplate_header();
-	acpigen_write_register(&addr);
-	acpigen_write_resourcetemplate_footer();
+	acpigen_write_register_resource(&addr);
 
 	/* StatusRegister */
-	acpigen_write_resourcetemplate_header();
-	acpigen_write_register(&addr);
-	acpigen_write_resourcetemplate_footer();
+	acpigen_write_register_resource(&addr);
 
 	acpigen_pop_len();
 }
@@ -725,9 +721,7 @@
 void acpigen_write_CST_package_entry(acpi_cstate_t *cstate)
 {
 	acpigen_write_package(4);
-	acpigen_write_resourcetemplate_header();
-	acpigen_write_register(&cstate->resource);
-	acpigen_write_resourcetemplate_footer();
+	acpigen_write_register_resource(&cstate->resource);
 	acpigen_write_dword(cstate->ctype);
 	acpigen_write_dword(cstate->latency);
 	acpigen_write_dword(cstate->power);
@@ -827,7 +821,7 @@
 	acpigen_emit_dword(size);
 }
 
-void acpigen_write_register(acpi_addr_t *addr)
+static void acpigen_write_register(const acpi_addr_t *addr)
 {
 	acpigen_emit_byte(0x82);		/* Register Descriptor */
 	acpigen_emit_byte(0x0c);		/* Register Length 7:0 */
@@ -840,6 +834,13 @@
 	acpigen_emit_dword(addr->addrh);	/* Register Address High */
 }
 
+void acpigen_write_register_resource(const acpi_addr_t *addr)
+{
+	acpigen_write_resourcetemplate_header();
+	acpigen_write_register(addr);
+	acpigen_write_resourcetemplate_footer();
+}
+
 void acpigen_write_irq(u16 mask)
 {
 	/*