OvmfPkg: CsmSupportLib: depend on OvmfPkg.dec explicitly

SVN r16375 (git commit 72a11001, "OvmfPkg: CsmSupportLib: Set/use platform
specific legacy interrupt device") added the

  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfHostBridgePciDevId

PCD to CsmSupportLib. Since that "namespace" GUID is declared in
OvmfPkg/OvmfPkg.dec, and we've not used anything from OvmfPkg/OvmfPkg.dec
in CsmSupportLib.inf thus far, this is a new [Packages] dependency and
must be named.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>

git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/OvmfPkg@16414 6f19259b-4bc3-4df7-8a09-765794883524