ARM: AM437x: Align HS device variant defconfig filename

Align the name of the defconfig file for high-security (HS) device variants
from the AM43xx family of SoCs with the corresponding name used for the
general purpose devices. This allows for easier cross-association of those
files and also provides room to grow from an HS device part number
perspective.

Furthermore, update and cleanup associated MAINTAINERS file.

Signed-off-by: Andreas Dannenberg <dannenberg@ti.com>
Cc: Lokesh Vutla <lokeshvutla@ti.com>
Cc: Madan Srinivas <madans@ti.com>
diff --git a/board/ti/am43xx/MAINTAINERS b/board/ti/am43xx/MAINTAINERS
index 3d40b17..83645ac 100644
--- a/board/ti/am43xx/MAINTAINERS
+++ b/board/ti/am43xx/MAINTAINERS
@@ -4,6 +4,7 @@
 F:	board/ti/am43xx/
 F:	include/configs/am43xx_evm.h
 F:	configs/am43xx_evm_defconfig
-F:	configs/am43xx_evm_qspiboot_defconfig
 F:	configs/am43xx_evm_ethboot_defconfig
+F:	configs/am43xx_evm_qspiboot_defconfig
 F:	configs/am43xx_evm_usbhost_boot_defconfig
+F:	configs/am43xx_hs_evm_defconfig