drm/xe: Allow to drop vram resizing

drm/xe: Allow to drop vram resizing

The default behavior if the LMEMBAR doesn't match the maximum possible
size is to try to resize it. However the user might want to keep, even
for testing the behavior with small BAR, whatever size was set via
sysfs. Change the module parameter to int and check for negative value.

Cc: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Link: https://lore.kernel.org/r/20250409-bar-resize-param-v1-1-75bf4df38aa0@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>