util: Do not use $(PWD) in Makefiles

util: Do not use $(PWD) in Makefiles

644e8cdf5ee7 ("util: Move the m5ops.h file to a shared directory")
added include/ to the include path for m5 Makefiles, based on
$(PWD): $(PWD)/../../include.

Unfortunately, this breaks when using `make -C <path>`, as -C does
not move PWD accordingly. The fix is simply to remove $(PWD), as a
relative path is just fine here.

Change-Id: Ia046c29761363b6670e52c52a604c7e70a6a305a
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: Ciro Santilli <ciro.santilli@arm.com>
Reviewed-by: Ciro Santilli <ciro.santilli@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/12844
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>