OvmfPkg/QemuFwCfgLib: generalize InternalQemuFwCfgDmaBytes() to SKIP op
OvmfPkg/QemuFwCfgLib: generalize InternalQemuFwCfgDmaBytes() to SKIP op

The fw_cfg DMA interface provides a simple method to skip over bytes in an
fw_cfg blob before reading or writing more bytes.
InternalQemuFwCfgDmaBytes() can support it easily, we just have to expose
the Control parameter more flexibly than the current "Write" BOOLEAN.

Cc: Jordan Justen <a79006884ba9cf5f4f7fcbb92a15b208780d8c97@intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=359
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <7437296077edea1cb64451c122c4dac071f0cfbc@redhat.com>
Reviewed-by: Ard Biesheuvel <66d3c5fdaeea7ff1f996ad04f2c45e08ab38e2f5@linaro.org>
Reviewed-by: Jordan Justen <a79006884ba9cf5f4f7fcbb92a15b208780d8c97@intel.com>

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