Refactored code to support INSTANCES as string

Modified code in meson build to support INSTANCES flag as string
type which is passed from machine layer bb file.

Tested: Tested and verified the INSTANCES value.

Signed-off-by: Jayashree Dhanapal <jayashree-d@hcl.com>
Change-Id: I91a7610157c30abf2cbc4783350d8b0a744a6ba9
diff --git a/meson_config.h.in b/meson_config.h.in
new file mode 100644
index 0000000..ff7109c
--- /dev/null
+++ b/meson_config.h.in
@@ -0,0 +1,3 @@
+#pragma once
+
+inline static const std::string hostInstances = @INSTANCES@;