linux-user,loongarch: move to syscalltbl file

linux-user,loongarch: move to syscalltbl file

Since kernel v6.11 loongarch has moved from syscall_nr.h file
to syscall.tbl (26a3b85bac08 ("loongarch: convert to generic syscall
table"))

Update linux-user scripts to be able to retrieve syscall numbers
from linux syscall.tbl instead of syscall_nr.h.
New syscall.tbl is imported from linux v6.11 using updated
scripts/update-syscalltbl.sh

Remove scripts/gensyscalls.sh that is now useless.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Message-ID: <20240920151034.859533-6-laurent@vivier.eu>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>