nand-utils: Fix integer overflow in nandflipbits.c

nand-utils: Fix integer overflow in nandflipbits.c

Report of the static analyzer:
The value of an arithmetic expression 'bit_to_flip->block * mtd.eb_size + blkoffs' is a subject to overflow because its operands are not cast to a larger data type before performing arith$

Corrections explained:
Prevent arithmetic overflow in OOB read operation
Resolved an issue where the calculation of the offset in the OOB read operation could overflow due to operands not being cast to a larger data type. Specifically, the multiplication of bi$

Triggers found by static analyzer Svace.

Signed-off-by: Anton Moryakov <ant.v.moryakov@gmail.com>
Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>