Convert CONFIG_BOOT_RETRY_TIME et al to Kconfig

This converts the following to Kconfig:
   CONFIG_BOOT_RETRY_TIME
   CONFIG_BOOT_RETRY_MIN
   CONFIG_RESET_TO_RETRY

We also introduce CONFIG_BOOT_RETRY to gate these options, and clean up
the associated Makefile entry and C code for picking default values of
CONFIG_BOOT_RETRY_MIN.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/am335x_shc_netboot_defconfig b/configs/am335x_shc_netboot_defconfig
index 2111495..37899df 100644
--- a/configs/am335x_shc_netboot_defconfig
+++ b/configs/am335x_shc_netboot_defconfig
@@ -24,6 +24,9 @@
 CONFIG_AUTOBOOT_PROMPT="Enter 'shc' to enter prompt (times out) %d \nEnter 'noautoboot' to enter prompt without timeout\n"
 CONFIG_AUTOBOOT_DELAY_STR="shc"
 CONFIG_AUTOBOOT_STOP_STR="noautoboot"
+CONFIG_BOOT_RETRY=y
+CONFIG_BOOT_RETRY_TIME=30
+CONFIG_RESET_TO_RETRY=y
 CONFIG_BOOTCOMMAND="run fusecmd; if run netboot; then echo Booting from network; else echo ERROR: Cannot boot from network!; panic; fi; "
 CONFIG_DEFAULT_FDT_FILE="am335x-shc"
 CONFIG_SYS_CONSOLE_INFO_QUIET=y