arm: dts: Fix build of am62a7 dtbs

am62a7 should be built with CONFIG_SOC_K3_AM62A7 not CONFIG_SOC_K3_AM625

Fixes: 6bdfa691 ("arm: dts: introduce am62a7 u-boot dtbs")
Cc: Bryan Brattlof <bb@ti.com>
Cc: Vignesh Raghavendra <vigneshr@ti.com>
Cc: Francesco Dolcini <francesco@dolcini.it>
Cc: Sjoerd Simons <sjoerd@collabora.com>
Cc: Wadim Egorov <w.egorov@phytec.de>
Reviewed-by: Bryan Brattlof <bb@ti.com>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Signed-off-by: Nishanth Menon <nm@ti.com>