libwacom: add missing dep for -devel subpkg

[chrysos349]

libwacom-devel-2.9.0 requires libevdev-devel as a dependency.

mutter which depends on libwacom-devel fails to build and spits out this error:

meson.build:284:17: ERROR: Dependency lookup for libwacom with method 'pkgconfig' failed: Could not generate cflags for libwacom:
Package libevdev was not found in the pkg-config search path.
Perhaps you should add the directory containing `libevdev.pc'
to the PKG_CONFIG_PATH environment variable
Package 'libevdev', required by 'libwacom', not found

Testing the changes

• I tested the changes in this PR: YES

Local build testing

• I built this PR locally for my native architecture, (x86_64)

[sgn]

This is wrong, libwacom only Requires.private: gudev-1.0, glib-2.0, libevdev. Hence, no.

[sgn]

Suggested change

	depends="libgudev-devel ${sourcepkg}>=${version}_${revision}
	libevdev-devel"
	depends="${sourcepkg}>=${version}_${revision}"

libwacom only Requires.private: gudev-1.0, glib-2.0, libevdev hence, it shouldn't depend on libgudev-devel either.

[sgn]

Hm, may be I was wrong, Requires.private: gudev-1.0, glib-2.0, libevdev cause pkg-config --cflags failure if it's not exists.

I think in libwacom case, it should be Libs.private instead.