systemc: Rename tlm_core header files to have a .hh extentension.

This makes those files more consistent with other headers in gem5. The
top level headers (tlm and tlm.h) and the tlm_utils headers were left
alone since the user might reasonably expect those to have a well known
name. The tlm_core headers by comparison are an implementation detail,
and users shouldn't include them directly by name.

Change-Id: Ibc82e8159e47717c79d76f50ed96fdd619294a06
Reviewed-on: https://gem5-review.googlesource.com/c/15067
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>

systemc: Include cstring in the tlm header file.

A lot of TLM implementation assumes the string functions (memcpy,
memset, etc) are available, but don't include cstring. Lets do that
for them to avoid having to fix up a lot of places.

Change-Id: I1f26d3a227fe2cefc2613e24cbb0333216e46ee9
Reviewed-on: https://gem5-review.googlesource.com/c/15060
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>

systemc: Remove redundant tlm_ prefixes from file names.

We already know those files belong to tlm because of the directory
they're in. Removing the prefix makes the paths of the headers less
enormously long.

Change-Id: I869e58fae904162f353bb31f4c0919fba08dffa6
Reviewed-on: https://gem5-review.googlesource.com/c/15059
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>

systemc: Fix style issues in the TLM header files.

Change-Id: Id12ffb9b56b3887afcf30120f81ce5eb75a5987b
Reviewed-on: https://gem5-review.googlesource.com/c/15057
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>

systemc: Initial import of TLM headers from Accellera.

These headers will need to be cleaned up and have some Accellera
specific quirks ironed out of them, but I'll do that in a later change
to make it clear what those changes are.

Change-Id: Ia4e08633ab552b4c616c66c9b7e2bbd78ebfe7b9
Reviewed-on: https://gem5-review.googlesource.com/c/15055
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>