configs: ls1012afrwy: drop env qspi_bootcmd

Drop useless environment variable installer and qspi_bootcmd
for ls1012afrwy.
Only 2 MB nor flash in ls1012afrwy. So cannot get kernel(30 MB) from
the nor flash, then drop it.

Signed-off-by: Biwen Li <biwen.li@nxp.com>
Signed-off-by: Priyanka Jain <priyanka.jain@nxp.com>