lib/bch: fix signed left-shift undefined behavior

lib/bch: fix signed left-shift undefined behavior

Patch series "lib/bch: fix undefined behavior from signed left-shifts".

Fix two instances of undefined behavior in lib/bch.c caused by
left-shifting signed integers into or past the sign bit.

While the kernel's -fno-strict-overflow flag prevents miscompilation
today, these are formally UB per C11 6.5.7p4 and trivial to fix.

This patch (of 2):

Use 1u instead of 1 to avoid undefined behavior when left-shifting into
the sign bit of a signed int.  deg() can return up to 31, and 1 << 31 is
UB per C11.

Link: https://lkml.kernel.org/r/20260318074806.16527-2-objecting@objecting.org
Signed-off-by: Josh Law <objecting@objecting.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Ivan Djelic <ivan.djelic@parrot.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>