package/boost: fix patch formatting issue

Commit ea38acd1 ("package/boost:
backport development branch changes to fix MIPS64 build failure")
introduced a patch formatting issue detected by check-package. This
commit fixes this issue.

Fixes:

  package/boost/0001-Improve-modfunc-performance.patch:4: generate your patches with 'git format-patch -N'

  https://gitlab.com/buildroot.org/buildroot/-/jobs/3287511158



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>