board: am57xx: Rename TARGET_BEAGLE_X15 as TARGET_AM57XX_EVM

board/am57xx supports all boards based on am57xx. Rename the taget
as TARGET_AM57XX_EVM.

Fixes: 74cc8b097d9af ("board: ti: beagle_x15: Rename to indicate support for TI am57xx evms")
Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
diff --git a/configs/am57xx_evm_nodt_defconfig b/configs/am57xx_evm_nodt_defconfig
index 1cf82d2..4c5a0de 100644
--- a/configs/am57xx_evm_nodt_defconfig
+++ b/configs/am57xx_evm_nodt_defconfig
@@ -1,6 +1,6 @@
 CONFIG_ARM=y
 CONFIG_OMAP54XX=y
-CONFIG_TARGET_BEAGLE_X15=y
+CONFIG_TARGET_AM57XX_EVM=y
 CONFIG_SPL=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y