rseq: Increase AT_VECTOR_SIZE_BASE to match rseq auxvec entries

Two new auxiliary vector entries are introduced for rseq without
matching increment of the AT_VECTOR_SIZE_BASE, which causes failures
with CONFIG_HARDENED_USERCOPY=y.

Fixes: 317c8194 ("rseq: Introduce feature size and alignment ELF auxiliary vector entries")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20230104192054.34046-1-mathieu.desnoyers@efficios.com