select: Fix unbalanced user_access_end()

select: Fix unbalanced user_access_end()

While working on implementing user access validation on powerpc
I got the following warnings on a pmac32_defconfig build:

	  CC      fs/select.o
	fs/select.o: warning: objtool: sys_pselect6+0x1bc: redundant UACCESS disable
	fs/select.o: warning: objtool: sys_pselect6_time32+0x1bc: redundant UACCESS disable

On powerpc/32s, user_read_access_begin/end() are no-ops, but the
failure path has a user_access_end() instead of user_read_access_end()
which means an access end without any prior access begin.

Replace that user_access_end() by user_read_access_end().

Fixes: 7e71609f64ec ("pselect6() and friends: take handling the combined 6th/7th args into helper")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Link: https://lore.kernel.org/r/a7139e28d767a13e667ee3c79599a8047222ef36.1736751221.git.christophe.leroy@csgroup.eu
Signed-off-by: Christian Brauner <brauner@kernel.org>