net: ipa: kill definition of TRE_FLAGS_IEOB_FMASK

In "gsi_trans.c", the field mask TRE_FLAGS_IEOB_FMASK is defined but
never used.  Although there's no harm in defining this, remove it
for now and redefine it at some future date if it becomes needed.
This is warned about if "W=2" is added to the build command.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>