hsail: Fix a warning/build failure for HSAIL_X86.

hsail: Fix a warning/build failure for HSAIL_X86.

The Bitselect operation definition used ~ to invert the bits of a mask
value, but if that mask value is of type bool, that generates a
warning. This change casts that value to a uint64_t so that it can
always have ~ applied to it.

Change-Id: I7fbfc6ff264bc32a265f2724c772b8fae08590f7
Reviewed-on: https://gem5-review.googlesource.com/c/14655
Reviewed-by: Brandon Potter <Brandon.Potter@amd.com>
Maintainer: Gabe Black <gabeblack@google.com>