ARM: shmobile: r8a7790/lager dts: Rename label spi to qspi, add spi0 alias

Prepare for the advent of MSIOF SPI, which will be spi1 to spi4.

Signed-off-by: Geert Uytterhoeven <geert+renesas@linux-m68k.org>
Acked-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>