Initializer of a static member in union.

It is just me or does anybody have the same build error without
this patch?
------
src/arch/x86/boot/acpigen.c: In function 'acpigen_write_empty_PTC':
src/arch/x86/boot/acpigen.c:347:3: error: unknown field 'resv'
specified in initializer
src/arch/x86/boot/acpigen.c:347:3: warning: missing braces around
 initializer
src/arch/x86/boot/acpigen.c:347:3⚠️ (near initialization
 for 'addr.<anonymous>')
-------

Anyway, I believe at least this will cause warnings.
"resv" is a member of a union, not of acpi_addr_t. So it should be
wrapped by a brace in the initializer.

Change-Id: I72624386816c987d5bb2d3a3a64c7c58eb9af389
Signed-off-by: Zheng Bao <zheng.bao@amd.com>
Signed-off-by: zbao <fishbaozi@gmail.com>
Reviewed-on: http://review.coreboot.org/1056
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Marc Jones <marcj303@gmail.com>

src/arch/x86/boot/acpigen.c

@@ -344,7 +344,9 @@ int acpigen_write_empty_PTC(void)
 		.space_id   = ACPI_ADDRESS_SPACE_FIXED,
 		.bit_width  = 0,
 		.bit_offset = 0,
-		.resv       = 0,
+		{
+			.resv       = 0
+		},
 		.addrl      = 0,
 		.addrh      = 0,
 	};