systemtap: upgrade 4.9 -> 5.0

systemtap: upgrade 4.9 -> 5.0

Similar to 4.9 release, in 5.0 release release-5.0 tag is off any branch,
release-5.0a tag e72dc118e563c645d93a1a2d771e8d90e8fec1ae is on the master
branch. Use this value for SRCREV and add catch up patch,
0001-prerelease-datestamp-fixes.patch, to bring source up to release-5.0 tag
level. Remove 0001-prerelease-datestamp-fixes.patch in next upgrade.

Signed-off-by: Victor Kamensky <victor.kamensky7@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>