msm: 8998: Replace cobalt with 8998

Update the code name from msmcobalt to msm8998. As a result, update
the filename containing "cobalt" and files content containing "cobalt".

CRs-Fixed: 1070840
Change-Id: I2c7b95e3e2a2fec7730724da9eeb86a39a77faf1
Signed-off-by: Runmin Wang <runminw@codeaurora.org>
Signed-off-by: Kyle Yan <kyan@codeaurora.org>
Signed-off-by: Jeevan Shriram <jshriram@codeaurora.org>