binfmt_elf_fdpic: remove the set_fs(KERNEL_DS) in elf_fdpic_core_dump

There is no logic in elf_fdpic_core_dump itself or in the various arch
helpers called from it which use uaccess routines on kernel pointers
except for the file writes thate are nicely encapsulated by using
__kernel_write in dump_emit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>