at91: move arch-at91sam9 to arch-at91

Makefile

cpu/arm926ejs/at91/Makefile

cpu/arm926ejs/at91/config.mk

cpu/arm926ejs/at91/ether.c

cpu/arm926ejs/at91/lowlevel_init.S

cpu/arm926ejs/at91/spi.c

cpu/arm926ejs/at91/timer.c

cpu/arm926ejs/at91/u-boot.lds

cpu/arm926ejs/at91/usb.c

include/asm-arm/arch-at91/at91_pio.h

include/asm-arm/arch-at91/at91_pit.h

include/asm-arm/arch-at91/at91_pmc.h

include/asm-arm/arch-at91/at91_rstc.h

include/asm-arm/arch-at91/at91_spi.h

include/asm-arm/arch-at91/at91cap9.h

include/asm-arm/arch-at91/at91cap9_matrix.h

include/asm-arm/arch-at91/at91sam9260.h

include/asm-arm/arch-at91/at91sam9260_matrix.h

include/asm-arm/arch-at91/at91sam9261.h

include/asm-arm/arch-at91/at91sam9261_matrix.h