HAVE_ARCH_HUGE_VMAP also works on XIP kernel, so remove its dependency on
!XIP_KERNEL.

This also fixes a boot problem for XIP kernel introduced by the commit in
"Fixes:". This commit used huge page mapping for vmemmap, but huge page
vmap was not enabled for XIP kernel.

Fixes: ff172d48 ("riscv: Use hugepage mappings for vmemmap")
Signed-off-by: Nam Cao <namcao@linutronix.de>
Cc: <stable@vger.kernel.org>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20240526110104.470429-1-namcao@linutronix.deSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>