AMD Inagua: PlatformGnbPcie.c: Allocate exact needed size for buffer

The following commit

    commit d0790694b0
    Author: Kerry Sheh <shekairui@gmail.com>
    Date:   Thu Jan 19 13:18:37 2012 +0800

        Inagua: Inagua GNB ddi lanes and pcie lanes config update

        Reviewed-on: http://review.coreboot.org/544

assigns lanes 4 and 5 to PCI device number 4, but does not
adapt the rest of the code.

After the commit above, the array `PortList []` only has four
elements, but the buffer size `AllocHeapParams.RequestedBufferSize`
is set to a size as it still has five elements.

Correct that by setting the size for four array elements.

[1] http://review.coreboot.org/#/c/3239/3/src/mainboard/amd/inagua/PlatformGnbPcie.c

Change-Id: I3ff07f308ffd417d2bf73117eda9da2a1a05f199
Reported-by: Bruce Griffith <Bruce.Griffith@se-eng.com>
Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-on: http://review.coreboot.org/3246
Tested-by: build bot (Jenkins)
Reviewed-by: Bruce Griffith <Bruce.Griffith@se-eng.com>

src/mainboard/amd/inagua/PlatformGnbPcie.c

@@ -109,7 +109,7 @@ OemCustomizeInitEarly (
 	// Allocate buffer for PCIe_COMPLEX_DESCRIPTOR , PCIe_PORT_DESCRIPTOR and PCIe_DDI_DESCRIPTOR
 	//
 	AllocHeapParams.RequestedBufferSize = sizeof (PCIe_COMPLEX_DESCRIPTOR)  +
-			sizeof (PCIe_PORT_DESCRIPTOR) * 5 +
+			sizeof (PCIe_PORT_DESCRIPTOR) * 4 +
 			sizeof (PCIe_DDI_DESCRIPTOR) * 2;
 
 	AllocHeapParams.BufferHandle = AMD_MEM_MISC_HANDLES_START;