mapper: meson: minor formatting change

Use a multiline format to facilitate longer descriptions as future
options are defined.

Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
Change-Id: I06040a302d291829eed0d514c74ce221de06803f
diff --git a/meson_options.txt b/meson_options.txt
index cdf492c..71f7241 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -1 +1,6 @@
-option('tests', type: 'feature', description: 'Build tests', value: 'enabled')
+option(
+    'tests',
+    type: 'feature',
+    value: 'enabled',
+    description: 'Build tests'
+)