[MLIR] NFC: Rename mcuMemHostRegister* to mgpuMemHostRegister* to make it consistent...

[MLIR] NFC: Rename mcuMemHostRegister* to mgpuMemHostRegister* to make it consistent with the other cuda-runner functions and ROCm.

Summary: Rename mcuMemHostRegister* to mgpuMemHostRegister*.

Reviewers: herhut

Reviewed By: herhut

Subscribers: yaxunl, mehdi_amini, rriddle, jpienaar, shauheen, antiagainst, nicolasvasilache, arpith-jacob, mgester, lucyrfox, aartbik, liufengdb, stephenneuendorffer, Joonsoo, grosul1, Kayjukh, jurahul, msifontes

Tags: #mlir

Differential Revision: https://reviews.llvm.org/D84583