arm: lpc32xx: move SoC to mach-lpc32xx

Following the example of most other SoCs in arch/$(ARCH)/cpu/$(CPU)/$(SOC)
move the lpc32xx code from arch/arm/cpu/arm926ejs/lpc32xx to
arch/arm/mach-lpc32xx.

Following the checklist from
commit 01f14456 ("ARM: prepare for moving SoC sources into mach-*"):

    [1] move files from arch/arm/cpu/arm926ejs/lpc32xx to arch/arm/mach-lpx32xx
    [2] add machine entry to arch/arm/Makefile
    [3] remove "obj-y += ..." from arch/arm/cpu/arm926ejs/Makefile
    [4] fix the Kconfig file path in arch/arm/Kconfig
    [5] (no MAINTAINERS update)

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Trevor Woerner <twoerner@gmail.com>