vendorcode/amd/agesa/f16kb/*/PcieComplexDataKB.c: Implicit truncation

Clang complains:
 "implicit truncation from 'int' to bitfield changes value from -1 to 15"

-1 is define in 'c11std 6.3.1.3p2' as:

 [Signed and unsigned integers] Otherwise, if the new type is unsigned,
 the value is converted by repeatedly adding or subtracting one
 more than the maximum value that can be represented in the new type
 until the value is in the range of the new type.60)
 FOOTNOTE.60 The rules describe arithmetic on the mathem...

This is "0xFF" on Mullins and "0xF" in this case. Clang seems to
complain about this two's complement in a bitfield as being truncated.
As the bitfield is 4 bits wide, (a maximum of 15 decimal), we set the
field as '0x0F'. Ideally this field /should/ be set to 'UINT8_MAX' however
we still have silly truncation warnings.

Change-Id: Ib7476d453ffd932bb911e638117cf9f56f71f269
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/7719
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Tested-by: build bot (Jenkins)