powerpc/eeh: Fix spelling of the word "auxillary" and update comment

Fix spelling of the word "auxillary" in arch/powerpc/kernel/eeh_pe.c
and arch/powerpc/include/asm/eeh.h.

Also update the eeh_set_pe_aux_size() comment to include the units.

Signed-off-by: Ghanshyam Agrawal <ghanshyam1898@gmail.com>
[mpe: Squash into one commit]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/2ab034609285b21c309cd8ab26c937c846d37ee7.1703756365.git.ghanshyam1898@gmail.com