x86/platform/uv: Helper functions for allocating and freeing conversion tables

Add alloc_conv_table() and FREE_1_TO_1_TABLE() to reduce duplicated
code among the conversion tables we use.

Signed-off-by: Steve Wahl <steve.wahl@hpe.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20230519190752.3297140-6-steve.wahl%40hpe.com