no-MMU: expose vmalloc_huge() for alloc_large_system_hash()

It turns out that for the CONFIG_MMU=n builds, vmalloc_huge() was never
defined, since it's defined in mm/vmalloc.c, which doesn't get built for
the no-MMU configurations.

Just implement the trivial wrapper for the no-MMU case too.  In fact,
just make it an alias to the existing __vmalloc() function that has the
same signature.

Link: https://lore.kernel.org/all/CAMuHMdVdx2V1uhv_152Sw3_z2xE0spiaWp1d6Ko8-rYmAxUBAg@mail.gmail.com/
Link: https://lore.kernel.org/all/CA+G9fYscb1y4a17Sf5G_Aibt+WuSf-ks_Qjw9tYFy=A4sjCEug@mail.gmail.com/
Link: https://lore.kernel.org/all/[email protected]/
Reported-and-tested-by: Linux Kernel Functional Testing <[email protected]>
Reported-and-tested-by: Geert Uytterhoeven <[email protected]>
Reported-by: Sudip Mukherjee <[email protected]>
Reported-by: Guenter Roeck <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: torvalds

mm/nommu.c

@@ -226,6 +226,8 @@ void *vmalloc(unsigned long size)
 }
 EXPORT_SYMBOL(vmalloc);
 
+void *vmalloc_huge(unsigned long size, gfp_t gfp_mask) __weak __alias(__vmalloc);
+
 /*
  *	vzalloc - allocate virtually contiguous memory with zero fill
  *