alpha/boot: Add .gitignore ignoring vmlinux kernel image

Building the kernel creates the untracked kernel image file 'vmlinux' in 'arch/alpha/boot/' - ignore it by adding a new local .gitignore file.

---
 arch/alpha/boot/.gitignore | 2 ++
 1 file changed, 2 insertions(+)
 create mode 100644 arch/alpha/boot/.gitignore

new file mode 100644
index 000000000000..4abc9c8ab7d3
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+vmlinux

2.51.0