mtd: rawnand: qcom: Fix build issue on x86 architecture

Fix a buffer overflow issue in qcom_clear_bam_transaction by using
struct_group to group related fields and avoid FORTIFY_SOURCE warnings.

On x86 architecture, the following error occurs due to warnings being
treated as errors:

In function ‘fortify_memset_chk’,
    inlined from ‘qcom_clear_bam_transaction’ at
drivers/mtd/nand/qpic_common.c:88:2:
./include/linux/fortify-string.h:480:25: error: call to ‘__write_overflow_field’
declared with attribute warning: detected write beyond size of field
(1st parameter); maybe use struct_group()? [-Werror=attribute-warning]
  480 |                         __write_overflow_field(p_size_field, size);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  LD [M]  drivers/mtd/nand/nandcore.o
  CC [M]  drivers/w1/masters/mxc_w1.o
cc1: all warnings being treated as errors

This patch addresses the issue by grouping the related fields in
struct bam_transaction using struct_group and updating the memset call
accordingly.

Fixes: 8c52932d ("mtd: rawnand: qcom: cleanup qcom_nandc driver")
Signed-off-by: Md Sadre Alam <quic_mdalam@quicinc.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>