PCI: endpoint: Rename 'epf_bar::aligned_size' to 'epf_bar:mem_size'

PCI: endpoint: Rename 'epf_bar::aligned_size' to 'epf_bar:mem_size'

Rename the member 'epf_bar::aligned_size' to 'epf_bar::mem_size' to better
reflect its purpose. 'aligned_size' was misleading, as it actually
represents the backing memory size allocated for the BAR rather than the
aligned size.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Reviewed-by: Niklas Cassel <cassel@kernel.org>
Link: https://patch.msgid.link/20251015-vntb_msi_doorbell-v6-1-9230298b1910@nxp.com