OvmfPkg/QemuFlashFvbServicesRuntimeDxe: list "FwBlockService.h" in INFs

OvmfPkg/QemuFlashFvbServicesRuntimeDxe: list "FwBlockService.h" in INFs

Among other things, the header file provides (extern) declarations for the
EFI_FIRMWARE_VOLUME_BLOCK_PROTOCOL member functions that are defined in
"FwBlockService.c". This way "mFvbDeviceTemplate.FwVolBlockInstance" can
be initialized near the top of "FwBlockService.c", ahead of the member
function definitions.

"FwBlockService.c" is linked into both the DXE_SMM_DRIVER and the
DXE_RUNTIME_DRIVER builds of this module, thus list the header file in
both INF files.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Suggested-by: Michael Kinney <michael.d.kinney@intel.com>
Ref: http://mid.mail-archive.com/E92EE9817A31E24EB0585FDF735412F56327F7D3@ORSMSX113.amr.corp.intel.com
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>