sysctl: Refactor base paths registrations

This is part of the general push to deprecate register_sysctl_paths and
register_sysctl_table. The old way of doing this through
register_sysctl_base and DECLARE_SYSCTL_BASE macro is replaced with a
call to register_sysctl_init. The 5 base paths affected are: "kernel",
"vm", "debug", "dev" and "fs".

We remove the register_sysctl_base function and the DECLARE_SYSCTL_BASE
macro since they are no longer needed.

In order to quickly acertain that the paths did not actually change I
executed `find /proc/sys/ | sha1sum` and made sure that the sha was the
same before and after the commit.

We end up saving 563 bytes with this change:

./scripts/bloat-o-meter vmlinux.0.base vmlinux.1.refactor-base-paths
add/remove: 0/5 grow/shrink: 2/0 up/down: 77/-640 (-563)
Function                                     old     new   delta
sysctl_init_bases                             55     111     +56
init_fs_sysctls                               12      33     +21
vm_base_table                                128       -    -128
kernel_base_table                            128       -    -128
fs_base_table                                128       -    -128
dev_base_table                               128       -    -128
debug_base_table                             128       -    -128
Total: Before=21258215, After=21257652, chg -0.00%

[mcgrof: modified to use register_sysctl_init() over register_sysctl()
 and add bloat-o-meter stats]

Signed-off-by: Joel Granados <j.granados@samsung.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Tested-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Christian Brauner <brauner@kernel.org>