OvmfPkg/AcpiPlatformDxe: don't #include "QemuLoader.h" in "Qemu.c"

We added initial support for QEMU's ACPI linker/loader in commit
a618eaa1f45d ("OvmfPkg: AcpiPlatformDxe: don't rely on unstable QEMU
interface", 2014-06-19). This commit defined the command structures in the
new file "QemuLoader.h", and #included the header in the preexistent
"Qemu.c" file, where the initial command script processing loop was being
implemented.

In commit 14b0faadfc87 ("OvmfPkg/AcpiPlatformDxe: Split QEMU fw-cfg into a
new file", 2015-02-02), we extracted the -- by then, more advanced --
linker/loader script processing from "Qemu.c" to "QemuFwCfgAcpi.c".
"Qemu.c" was going to need "QemuLoader.h" no longer, but we forgot to make
the #include directive unique to the new "QemuFwCfgAcpi.c" file. Do it
now.

Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Julien Grall <julien.grall@linaro.org>
Cc: Phil Dennis-Jordan <phil@philjordan.eu>
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>