[SPARC32]: Mark srmmu_nocache_init as __init.

Fix these 2.6.19-rc1 build warnings from modpost:

WARNING: vmlinux - Section mismatch: reference to .init.text:__alloc_bootmem from .text between 'srmmu_nocache_init' (at offset 0x1a0f8) and 'srmmu_mmu_info'
WARNING: vmlinux - Section mismatch: reference to .init.text:__alloc_bootmem from .text between 'srmmu_nocache_init' (at offset 0x1a118) and 'srmmu_mmu_info'
WARNING: vmlinux - Section mismatch: reference to .init.text:srmmu_early_allocate_ptable_skeleton from .text between 'srmmu_nocache_init' (at offset 0x1a188) and 'srmmu_mmu_info'

Signed-off-by: Martin Habets <errandir_news@mph.eclipse.co.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>