phy_tesla.c: Fix compilation errors for TESLA PHYs

[MikeLooijmans]

Fix missing headers and methods that aren't critical. Undefined symbols, doubly defined methods, defined but unused symbols.

[jackyh2020]

#define VTSS_TESLA 1 /* Enables support of VSC8504, VSC8552 */
Seeing compile warning message with above define that is required for TELSA chip.

VTSS_TESLA_A and VTSS_TESLA_B only required for older chip revisions.
VTSS_TESLA_D is to be defined for current production revision.

[topic-buildserver]

I have no idea what you mean by that comment. To activate the TESLA PHY support you'd need to do that, yes, but without merging this PR that results in a compilation failure. This PR fixes the failures and makes the TESLA PHY work (if you #define it).