am43xx_evm: Add qspiboot target

The ePOS EVM and EVM SK have QSPI as an option to boot.  Add a qspiboot
target that utilizes QSPI for env and so forth as an example of best
practices.  As QSPI is booted from directly we need to chang
CONFIG_SYS_TEXT_BASE.

Note that on ePOS EVM the QSPI and NAND are mutually exclusive choices
we need to handle that elsewhere, once NAND support is also added.

Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
Signed-off-by: Tom Rini <trini@ti.com>
diff --git a/board/ti/am43xx/Makefile b/board/ti/am43xx/Makefile
index cb5fe88..36ecb30 100644
--- a/board/ti/am43xx/Makefile
+++ b/board/ti/am43xx/Makefile
@@ -6,7 +6,7 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-ifdef CONFIG_SPL_BUILD
+ifeq ($(CONFIG_SKIP_LOWLEVEL_INIT),)
 obj-y	:= mux.o
 endif