app: aboot: add target boot params

Make aboot to get target specific boot params so that boot params can be
appended to kernel command line.
Also fix mdmkrypton to provide 'root=' as target boot param to get rid of
hardcoded root device name from boot image.

Change-Id: I10129a0249438b8bc7da1ea8a8c0097489e6e289
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
diff --git a/platform/init.c b/platform/init.c
index 5001373..7efea46 100644
--- a/platform/init.c
+++ b/platform/init.c
@@ -105,3 +105,9 @@
 __WEAK void clock_config_cdc(uint8_t slot)
 {
 }
+
+__WEAK int get_target_boot_params(const char *cmdline, const char *part,
+				  char *buf, int buflen)
+{
+	return -1;
+}