drivers: i2c: xilinx_axi: Remove nested spinlock

Removed nested spinlock acquisition in i2c_xilinx_axi_write to prevent
ztest failures due to invalid spinlock usage.
Ensured spinlocks are not consecutively acquired without unlocking,
preventing potential deadlocks.

Signed-off-by: Ajay Neeli <ajay.neeli@amd.com>