gnu: ncurses/gpm: Move to (gnu packages ncurses).

This is needed to avoid compilation problems caused by the cyclic dependency
between (gnu packages ncurses) and (gnu packages linux).

* gnu/packages/linux.scm (ncurses/gpm): Move to ...
* gnu/packages/ncurses.scm (ncurses/gpm): ... here.  Fix misleading
indentation.  Add (gnu packages linux) to the module imports.

gnu/packages/linux.scm

@@ -3013,18 +3013,6 @@ applications running on the Linux console.  It allows users to select items
 and copy/paste text in the console and in xterm.")
     (license license:gpl2+)))
 
-(define-public ncurses/gpm
-  (package/inherit ncurses
-    (name "ncurses-with-gpm")
-    (arguments
-        (substitute-keyword-arguments (package-arguments ncurses)
-         ((#:configure-flags cf)
-          `(cons (string-append "--with-gpm="
-                                (assoc-ref %build-inputs "gpm")
-                                "/lib/libgpm.so.2") ,cf))))
-    (inputs
-     `(("gpm" ,gpm)))))
-
 (define-public btrfs-progs
   (package
     (name "btrfs-progs")

gnu/packages/ncurses.scm

@@ -32,6 +32,7 @@
   #:use-module (gnu packages perl)
   #:use-module (gnu packages pkg-config)
   #:use-module (gnu packages swig)
+  #:use-module (gnu packages linux)
   #:use-module (guix utils))
 
 (define-public ncurses
@@ -200,6 +201,19 @@ ncursesw library provides wide character support.")
             (origin-patches (package-source ncurses))
             (search-patches "ncurses-CVE-2017-10684-10685.patch")))))))
 
+(define-public ncurses/gpm
+  (package/inherit ncurses
+    (name "ncurses-with-gpm")
+    (arguments
+     (substitute-keyword-arguments (package-arguments ncurses)
+       ((#:configure-flags cf)
+        `(cons (string-append "--with-gpm="
+                              (assoc-ref %build-inputs "gpm")
+                              "/lib/libgpm.so.2")
+               ,cf))))
+    (inputs
+     `(("gpm" ,gpm)))))
+
 (define-public dialog
   (package
     (name "dialog")