mips: cavium-octeon: Move octeon-crypto.c into parent dir

Since octeon-crypto.c is the only remaining source file in
arch/mips/cavium-octeon/crypto/, move it into its parent directory
arch/mips/cavium-octeon/.  Then remove the directory
arch/mips/cavium-octeon/crypto/, including its Makefile.

Link: https://lore.kernel.org/r/20250805222855.10362-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

arch/mips/cavium-octeon/Makefile

@@ -11,9 +11,9 @@
 
 obj-y := cpu.o setup.o octeon-platform.o octeon-irq.o csrc-octeon.o
 obj-y += dma-octeon.o
+obj-y += octeon-crypto.o
 obj-y += octeon-memcpy.o
 obj-y += executive/
-obj-y += crypto/
 
 obj-$(CONFIG_MTD)		      += flash_setup.o
 obj-$(CONFIG_SMP)		      += smp.o

arch/mips/cavium-octeon/crypto/Makefile

@@ -1,6 +0,0 @@
-# SPDX-License-Identifier: GPL-2.0
-#
-# OCTEON-specific crypto modules.
-#
-
-obj-y += octeon-crypto.o