LoongArch: Fix section mismatch warning

init_numa_memory() is annotated __init and not used by any module,
thus don't export it.

Remove not needed EXPORT_SYMBOL for init_numa_memory() to fix the
following section mismatch warning:

  MODPOST vmlinux.symvers
WARNING: modpost: vmlinux.o(___ksymtab+init_numa_memory+0x0): Section mismatch in reference
from the variable __ksymtab_init_numa_memory to the function .init.text:init_numa_memory()
The symbol init_numa_memory is exported and annotated __init
Fix this by removing the __init annotation of init_numa_memory or drop the export.

This is build on Linux 5.19-rc4.

Fixes: d4b6f156 ("LoongArch: Add Non-Uniform Memory Access (NUMA) support")
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>