manifest: Update reference for hal_silabs

The test benchmark.kernel.footprints.pm currently generate these warnings
during the link:

    [204/209] Linking C executable zephyr/zephyr_pre0.elf
    .../ld.bfd: warning: orphan section `.udma_addr1' from \
        `zephyr/libzephyr.a(UDMA.c.obj)' being placed in   \
        section `.udma_addr1'
    [209/209] Linking C executable zephyr/zephyr.elf
    .../ld.bfd: warning: orphan section `.udma_addr1' from \
        `zephyr/libzephyr.a(UDMA.c.obj)' being placed in   \
        section `.udma_addr1'

Last version of hal_silabs provide a workaround for this issue.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>