meson: Use boost as a dependency

Currently boost library is found via the 'cpp.find_library' call. With
this method local build of the project requires host to have the boost
libraries installed.
Since the meson have a subproject system to download missing
dependencies, rewrite boost requirement to a 'dependency' object. This
way it would be possible to build the project locally on the system
without the boost library installed.

Tested:
Both local meson build and Yocto build are performed successfully.

Change-Id: I082aeb1d6c09627ea53f58cb6cd375f080401d57
Signed-off-by: Konstantin Aladyshev <aladyshev22@gmail.com>
diff --git a/softoff/meson.build b/softoff/meson.build
index f34ad98..cdc5d03 100644
--- a/softoff/meson.build
+++ b/softoff/meson.build
@@ -6,7 +6,7 @@
   sdbusplus_dep,
   systemd,
   softoff_dbus,
-  boost_coroutine
+  boost
 ]
 
 softpower_lib = static_library(