Make Pals only return amount of memory requested

The PAL API previously allowed for returning more memory than asked for.
This was when the PAL performed the alignment work, now this is done in
large alloc, so removing from the PAL.

src/pal/pal_freebsd_kernel.h

@@ -61,9 +61,9 @@ namespace snmalloc
     }
 
     template<bool committed>
-    void* reserve(size_t* size, size_t align)
+    void* reserve(size_t size, size_t align)
     {
-      size_t request = *size;
+      size_t request = size;
       vm_offset_t addr;
       if (vmem_xalloc(
             kernel_arena,