Fix unaligned accesses with ldm/stm in ChaCha20 and Poly1305 ARM/NEON

Fix unaligned accesses with ldm/stm in ChaCha20 and Poly1305 ARM/NEON

* cipher/chacha20-armv7-neon.S (UNALIGNED_STMIA8)
(UNALIGNED_LDMIA4): New.
(_gcry_chacha20_armv7_neon_blocks): Use new helper macros instead of
ldm/stm instructions directly.
* cipher/poly1305-armv7-neon.S (UNALIGNED_LDMIA2)
(UNALIGNED_LDMIA4): New.
(_gcry_poly1305_armv7_neon_init_ext, _gcry_poly1305_armv7_neon_blocks)
(_gcry_poly1305_armv7_neon_finish_ext): Use new helper macros instead
of ldm instruction directly.
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Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>